How To Replace Intake Manifold GM 3800 3.8L: Pontiac Bonneville, Buick LeSabre, Pontiac Grand Prix, Buick Park Avenue

var gaJsHost = ((“https:” == document.location.protocol) ? “https://ssl.” : “http://www.”); document.write(unescape(“%3Cscript src=\\\\\'” + gaJsHost + “\\\\\’ type=\\\\\’text/javascript\\\\\’%3E%3C/script%3E”)); The upper intake manifold is a very common failure point on the venerable GM 3800 Series II Engine. Often when it begins to fail, the car will show the symptoms of a head gasket failure, however actual head gaskets failing on this engine is VERY rare. One of the first signs of the intake manifold failure is coolant loss, these intakes can leak internally into the engine, or externally near the thermostat housing. In extreme cases, the leak can get so bad internally that it can actually Hydro-lock (when an engine fills with so much liquid that the pistons cannot move up in their bore). This was the case on the example car I will show you today.In the case shown below, the owner of the car thought the head gaskets were bad, and it would need major repair or a new engine. After a quick inspection I knew it was only the intake manifold that was bad. The car had stalled on him, and would not turn over at all, acting like the engine was seized.

NOW AVAILABLE: Video Instructions Part 1

GM 3.8L Intake Manifold Replacement Instructions Part 2

Part 3-Removal Of The Fuel Injectors & Fuel Rail

Part 4-Removal & Explanation Of The Internal Components Of The Upper Engine

Part 5-Removing The Lower Intake Manifold & Alternator

Part 6-GM 3.8L Lower Intake Manifold Removed- Explanation Of The Valve Train & Middle Of The Engine

Part 7-Finishing Up

Before I start, here are the exact vehicles affected by this leak:

1995-2005 Pontiac Bonnville 3.8L

1998-2005 Chevy Monte Carlo 3.8L

2000-2005 Chevy Impala 3.8L

1996-2005 Buick Lesabre 3.8L

1996-2004 Buick Regal 3.8L

1995-2005 Buick Park Avenue 3.8L

1995-1997 Buick Riviera 3.8L

1995-1998 Olds Regency 3.8L

1995-1999 Oldsmobile Delta 88 3.8L

1996-1999 Oldsmobile LSS 3.8L

All 3.8L (3800) engines with VIN code K (8th digit of VIN) Non-supercharged

Before you tear into it, there are two important steps,

1) DISCONNECT the negative battery terminal

2) Drain any engine coolant that may still be in the car (there is a small drain near the bottom of the radiator). After these two steps, you must gain access to the intake manifold by removing some things that are in your way.

3) Remove the engine cover by turning the oil cap to loosen, then without pulling it off, continue to twist it counterclockwise, when it stops completely, pull the oil cap AND oil cap tube away from the engine. You can then lift the engine cover off of the engine.
SORRY IMAGES HAVE BEEN LOST, View video Instructions

Remove the air filter housing. Loosen the two Philips screws on the housing itself, then pull the throttle body hose end off. (Peel back the top of the hose, then work around until the whole thing comes loose) Disconnect the plug going into the intake hose, and remove whole assembly from car.

4) If the spark plug wires aren’t marked, mark which one goes where on the coil pack, and pull the three plug wires that run to the rear off of the coil, and let them fall to the rear of the engine bay.

5) Remove serpentine belt.

6) Loosen the three alternator bolts and remove wiring from back of alternator. Remove alternator and set aside. NOTE: To remove one of the bolts, you must remove a bracket which runs from the Alternator to just below the Ignition coils.TIP: There is a bolt which is hard to see just below the belt idler pulley.

7) Remove the 6 Fuel Injector electrical plugs, (Squeeze in on the metal locks and pull up) Remove the three electrical connectors going to the throttle body. Remove the electrical connector going to the MAP sensor (sits on top of the intake manifold near the alternator)

8) Remove all vacuum lines going to the throttle body and intake manifold.

9) Remove the fuel lines from the fuel rail. You will see two plastic lines going the the fuel rail, they are both held in by small plastic clips. To remove them, squeeze in on the bottom of the clips, then pull up on the fuel line. **CAUTION** There may be some residual fuel pressure in one of the lines, so remove the lines very slowly and carefully.

10) Remove Fuel Rail with injectors. There are four nuts which keep the fuel rail, and injectors in place. Once you remove those four 10mm nuts, carefully wiggle and pull upwards on the fuel rail, and the injectors will unseat themselves from the lower intake manifold, and the whole fuel rail will come out. Set aside.

11) Remove Throttle Body. There is a bracket which connects the throttle body to the cylinder head, this little bracket blocks access to one of the throttle body nuts. My trick is to remove the Bracket-to-throttle body bolt, then carefully pry the bracket back until you have enough access to reach the nut with a deep 10mm socket and extension. You can leave the throttle cables attached to the throttle body, and just position the entire assembly aside.At this point, you should have clear access to the entire upper intake manifold.

12) Remove all of the upper intake manifold bolts, and remove the intake from the car. If the intake does not want to separate from the lower, then you most likely missed a bolt. it should NOT require any prying to get it loose.

13)Now if the intake was leaking internally badly, you will likely see an alarmingly large puddle of coolant sitting inside the engine. It is CRUCIAL that you remove all of this coolant, use Paper towels or old rags to soak it all up. Clean the gasket mating surface on the lower intake manifold.TIP: It is very important to have a clean mating surface on the top of the lower intake manifold, or you may encounter leaks.

14) Snap the upper intake gasket into place onto the bottom of the new upper intake manifold and place the upper intake back onto the car, make sure all the bolt holes are aligned.

15) Install and tighten all the bolts in the following sequence NOTE: The Specified Torque is ONLY 89 INCH pounds,, which is less than 10 ft. pounds.. be very careful not to over-torque and risk cracking the new intake.

16) Reinstall all accessories and wiring, and fuel rail in the reverse order of removal. Refill the coolant system.

17) IMPORTANT STEP: If you saw ANY coolant at all inside the intake manifold upon removal,, you MUST replace the spark plugs. Also it is very important that you remove most of the coolant that may have entered the combustion chambers. Which is simple to do

17a) Remove all six spark plugs, and turn the engine over (pretend you’re starting it) for at least 30 seconds. Install six new spark plugs and you are good to go.

18) Start car and let idle for a while, check for any coolant leaks, carefully watch your temperature gage to make sure no overheating takes place. Once everything looks good, you are done!Congratulations, you just saved yourself Hundreds of Dollars by Replacing your own Intake Manifold on a 3.8 Liter 3800 Series II Car!

Written by Joe S.


About Josh

I help manage the site here at Auto Repair Instructions. If you are having problems, then I am the one to contact.

Posted on February 14, 2008, in Buick, Chevrolet, Intake Manifold Repair, Oldsmobile, Pontiac. Bookmark the permalink. 138 Comments.

  1. Thank you for this information. My sons 2002 Pontiac Grand Prix is a GTP with supercharger. Is it much more difficult when supercharge is on top of intake? If you have additional information on this replacement, would you eamil me. I read and artical that the GM on pre 2000 3800 has a defect that causes over heat on egr valve. Is it recommended to replace the whole intake manifold dorman. My son will be keeping this car for several years and we want to keep in running condition for 3-4 years. Thanks JIM

  2. thanks, saved my car. should oil be changed also?

  3. Upon bringing my 97 Grand Prix G.T.P. to the dealership this morning (for the supercharger/fire recall) the service mgr. advised me that the mechanic found that the lower intake and the rear valve cover gasket was leaking (probally making it even easier for cooleant to get into the engine oil, right?) So, I guess my question is similiar to #1 above, but also, would you get the new manifold/kit/gaskets from the dealership or aftermarket? I’m guessing the aftermarket would be cheaper, but the service mgr. said that if they did the work, it would be guaranteed for a year, is this because they have some confidence in their work or because their parts are better? He said it would cost $1100., so I’m thinking of doing this myself. Otherwise, this car has produced 141k miles of driving excitement. Also, what aftermarket brand drivebelts would you recommend or is that also something that should be bought from the dealer due to any possible quality shortfalls?

  4. It is easier to leave the throtttle body attached to the plenum and remove them together as one unit because of the difficulty of removing the lower nuts-Also would strongly advise to remove lower intake manifold and replace that gasket also and check the manifold for degradation cased by the infamous Dex-Cool

  5. I just completed the change of the upper intake plenum on my ’95 Buick Park Ave. I refered to ypu article a couple of times and I found it to have some good hints. One thing I would suggest an oil change after completing th job just to be safe. Thanks again for the info.

  6. Thanks for the information. It was very detailed with good hints, and allowed me to repair my 1997 Buick LeSabre for about $200 (versus the $1400 the rip-off man down the street wanted). One thing I advise is you get the updated upper manifold and EGR tube. The one I bought had blue (versus orange) gasketing for the coolant seals (I assume this is a better seal for that application….my old, failed unit had orange ones in that location). Also, you want to replace the EGR tube (near the throttle body) with a smaller diameter tube (should come in the upgrade kit). This prevent the hot exhasut gas (used during warm-up) from heating and distroiting the plastic manifold, as it is not in direct contact with the manifold. The only problem I had was the tube did not fit tightly into the lower manifold, so I added some indentations with a chisel along the large diameter, which created a tight fit.

  7. WOW! My 95 Bonneville seized up yesterday, with the “Low Coolant” light on and not much in the radiator. I was thinking the worst, but from what I have read today from several sights, this is exactly what I have. I am printing the instructions and am going to replace it tommorow, in the garrages parking lot where I had it towed, they know me, they had Better not mind… Thanks SO much for this info. Roy

  8. Thanks Good reading !! I’m in the middle of doing mine now.

  9. After completeing all the step up to putting the new manifold on the engine, shouldn’t I be able to turn the engine with a wrench. Before I put the new manifold back on the engine? URGENT

  10. you probably wouldn’t be able to turn it very easiy, as you are still creating a great deal of compression in the cylinders. you are also moving the rocker arms, the valve springs are pretty strong.

  11. If you want to turn the engine by hand (to ensure it’s not seized, etc) you can take the spark plugs out.

    That way, you aren’t trying to compress the air in the cylinder that’s on the compression phase (valves closed and piston moving upwards)

  12. I had this issue and put it back together. It seem to run fine but then it began blow smoke. I took it apart again and now I have lots of oil in the upper intake simulat to the amount of coolant last time. It seem to be comming from the same place as the coolant was. The EGR hole. I did not push that sleeve down there. should I have? Where is the oil comming from? Where can I find more answers.


  13. I m loosiing coolant some where ,how do I check upper manifold lleak.

  14. attention Joe S.
    thank you so much for your detailed information about the upper intake manifold.
    I kept posponing doing it, now i feel more secure thanks again.
    for info I also found an interesting information about and upper plenum and lower intake repair kit at:

  15. I too have a GTP with a leaking intake manifold (2001 with 86.000 miles). Is there further instruction available for replacing the intake manifold on a GTP? I’d read where two others have commented that they need to repair their GTP’s also, but haven’t seen any answers concerning it. Please advise, thank you for the info already posted!

  16. Thank you for your article

    I had never heard of an engine hydo-lock until this one. Wasn’t sure what the heck was going on. I knew it was water, but not sure how so much could get in there so fast and lock up the motor. The intake makes sense. I will be tearing into this today with your printed instructions. Thank you. Steve in Oregon.

  17. The procedure I used to replacing the upper intake manifold gasket was exactly as you described, but when I started the car and it flooded within seconds. Did I miss something? By the way, I think what you’re doing deserve great praise. Keep up the advise.

  18. I’m repairing a car with the same problem right now. Due to the engine taking on water, I pulled the lower intake and heads for inspection. I’ve heard the hydro locking can actually bend a rod. I just cleaned everything up and checked everything and believe I have a bent rod. 5 of the 6 pistons come up .025″ above the cylinder bore, the 6th sits .035″ below. Is this motor toast? Thanks

  19. So you want to know how to fix or keep you intake platoon from going in the can. Well, I’ll let you know what happened in my case and hope that it answers your questions.

    I have a 1997 Buick LeSabre Custom with a 3800 Series II V6. I overheated on the highway and was able to make it to a local parking lot. I turned off the car and found nothing in the way of what you would typically find in this case. The radiator hoses were cold! So I opened the radiator cap and found nothing, no coolant? I allowed the car to cool and then added water to see if I could find the leak. The car started but was running rough, so I hit the throttle body to give it some gas and it stalled. I tried to start the car again, and on the second attempt the car engine just stopped. Again I looked for a leak and found nothing… Where the hell did it go? Can you say hydra-lock? After a tow home, I pulled the spark plugs and the water came out. In fear that I may have warped or cracked the heads, I began making phone calls. I was not too concerned about any real engine damage, because the car was not under a running load at the time the water filled the cylinders.

    Soon it was time to start taking the engine apart and investigating the extent of damage. When I pulled off the platoon I found the top half of the intake was full of water. The gasket around the EGR stem had melted the platoon and gasket and allowed the water, I put in earlier, to be pulled into the cylinders. Now, I should say that the car had been running rough for a few days. That may very well have been the beginning sighs of the problems I was about to face. After spending some time on the net (like yourself) I did find a lot about the EGR problem melting this platoon. It’s seems to be a BIG issue with this engine and usually happens around the 100,000 mile mark,… but why? I could not find the answer. And this is why I’m taking the time to type it out.

    On the water pump manifold is a little plastic elbow tube. This manifold, on my car, has the tension pulley on it as well. The coolant start to brake down the plastic over time. At about this point in the engines life, 100,000 miles, the tube starts to give and weep. Most people don’t no this, because the weeping is burned up on the engine and caught in the guards under the car. So you have no sighs of a leak, like the big pond found under the car. So by the time it is caught, it’s too later. If you haven’t had the issue to the platoon yet, check the tube or just replace it. It cost about $14.00! Also it’s a dealer part. It’s a small price to pay and you only need to remove the alternator to get to it. The manifold is a little tricky to remove. The casting part that is inserted in the pump has an O-ring. With a little faunas, it dose come right off (Don’t forget the bolts too!) The whole job should take about 2 hours if you are taking your time. If the manifold is the issue, it’s about $155.00.

    With regards to the platoon, they give a an adapter to REPLACE the EGR stem. Measure the height, grab your vise-grips and twist the old one out. The new one is smaller than the old size. They give you two different sizes, depending on which one you have. The head on the replacement tube is the size you have now. They made the size smaller to create an air barrier between the plastic and the stem. Also the plastic water jackets are little thicker in this area.

    When all was said and done:
    Intake Platoon : $180.00
    Full Ejector O-rings : $20.00
    Water Manifold replacement parts : $15.00
    Radiator Hoses: $45.00
    Coolant: $20.00
    Tow truck to the house: $100.00

    Total: $380.00 + Beer to do it yourself.
    Not bad for what you may have spent at a repair shop!!

    I hope this story helps with your project and GOOD LUCK!

    -Tony (Tool & Die Maker)
    Livonia, Michigan

  20. Great info! I took the cables off the throttle body it took a few days to find how it done but I finnaly found out. When the upper intake was remove it wss as you said it was full of coolant. My intalke does not look like it got any cracks it looks as the gasket gave up I going to try that first. But final most repair shops wanted to install a use motor since it hydro lock and one shop would tear it down but it would cost $2,500 to start! The other shops were around $1800. Thanks again.

  21. hey wanted to say that i had already taken my upper and lower inatke gaskets off and about to replace them. however when i pulled my intake manifold off i noticed coolant and oil mixed togethor, my upper manifold was ok but i will replace it anyways and my lower manifold gaskets were just flat out no good. my question to you is how do i continue to let or make sure that their is no more water in my block causing it to not fire. now i havent put it all back togethor just yet but i have drained the radiator and the oil. if you could get back to me and let me know if theirs anything else i need to know or do before i start putting it all back togethor it would be much appreciated,,, thanks.

  22. 98 Buick Park Avenue… $1800 to replace the lower intake manifold when it failed at speed. Hydrolock occured. First shop wanted to replace the engine. After a tow to the dealer they fixed it for big cash. 70,000 miles. At 117,000 miles car is losing coolant. Changed the coolant and added stopleak. The next day a failure at speed again… thought it was a blown head gasket. No hydrolock, but rough idle and lots of white smoke. Still ignorant of this site I found a new garage who correctly diagnosed a failed upper intake manifold. $850 this time.

    I’m armed and dangerous now and ready to do it myself next time this car craps out. Thanks for the great service.

  23. I have a small leak on my 3800 just underneath the alternator. I washed the top of engine and it seems its leaking around the first bolt on the manifold by the alternator. I put some coolant dye and pressure tested the system. That’s the only spot I can see a few drops of coolant…around the bolt settling in the manifold pocket just under the bolt. Pressure los was about 5Lbs in approximately 7-8 minutes.

    Oil is clean and coolant los is about 3/4 cup in the last 10 days.

    My question is since there is no visible leak around the manifold gasket, is the bolt hole open into the coolant jacket and is it possible for the coolant to leak around the manifold bolt. Car is a 2001 Grand Prix with about 55K miles.

    Thanks for any help

  24. All the information is very good, I just replace the lower intake manifold on my 1999 gtp I want to know about the torque for the intake and the supercharger

  25. I replaced the plastic intake on my 3,8, now I’m getting a small puddle of coolant on the aluminum intake in one spot. Any suggestions? The motor was siezed, the shop said to junk it….boy were they wrong! Car runs like a champ!

  26. i have a 2002 gp 3.1 engine with this problem and dealer said it was the intake gaskets….does this engine have the same plastic intake plenum? after reading all the crap about these i wanted to replace but cant seem to find one of these for a 3.1 engine. any advice???

  27. I am currently working on my 1995 olds 88, 3.8 ltr. The upper manifold was leaking into the cylinders, also the lower intake gaskets were cracked in about 10 places. No water in the oil only into the cyls. Once you are doing the upper you might as well do the lower, its not that much more work. I also am changing out all bolts to rid my engine of the junk GM used. I am using Grade 8 Flange head type. I installed the lower today and they worked great. They are 5/16–18 thread–1 1/4 long. I bought them at our local hardware store. I am also changing the upper intake bolts, but they are mm, but I found a goo style and I beleive they will work. All other bolts will be Stainless. This not the cheapest way to go but I am sure it will be a better job than the dealer would do for a ton of money. Good Luck all.

  28. Dnnis Wallingsford

    Changed my manifold and now Engine won’t start. It ran but missed on cylinder 6 due to coolant leakage before manifold change. It has spark when cranked with plug pulled and held against a ground. Fuel squirts out of schrader valve when pushed and I can hear pump run when key is on. No codes and good cranking. All wires were reconnected properly. Help!!

  29. James J forest lake mn

    Changed my manifold and now Engine won’t start. It ran but missed on cylinder 6 due to coolant leakage before manifold change. It has spark when cranked with plug pulled and held against a ground. Fuel squirts out of schrader valve when pushed and I can hear pump run when key is on. No codes and good cranking. All wires were reconnected properly. Help!! i am having same problem

  30. Thanks, this really helped out alot, cost me 250.00 thats with the manifold, spark plugs, and wires , and the 25 $ tool rental for the Belt Tool, and also an o2 sensor on my car. and add 9.50 for lunch.

    Only problem I’m having now is that my car is surging while in drive at a stop light. If i shift in to N i don’t feel it, So i’m not sure If i missed something, or something else is going wrong with the car now.

  31. Just replaced the plenum and lower gaskets on a 97 Buick LeSabre. It had 174,000 on it before the plenum let go.This web site had great information and the directions were excellent. Bought the plenum from this site, which is a good value, and if you call them with any questions they are outstanding gietting getting back with you. cost for all this was around 230.00. This site saved a lot of money. Thanks all.

  32. The above pictures dont show up. Can someone please give the tightening sequence for the upper intake bolts?

  33. This page saved my bacon! It worked!

    What happened to the pictures? I couldn’t have done it without them.

  34. No offense to the DIYers out there, but I found a shop (a real shop, not a back yard) who did the job for $140 out the door. It was under $100 for the intake. If DIY works for you, do it. But know that the part cost varies greatly from one part store to the next, and so does the labor. If you prefer to have someone else do it, it CAN be done on the cheap. Especially if you do it before it is an issue like I did. During an oil change, the tech mentioned it and I took it to another place to have it done with no “just because” extras.
    2003 Monte SS
    Repaired at 90,000
    14,000 on repair

  35. Alexwebmaster

    Hello webmaster
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  36. This is great stuff — I could really use the pictures that are dead links. Can you email them?

  37. Tank you for this grat info — I too,could really use the pictures that are dead links. Can you email them?

  38. BuickRegalDriver

    One month ago I had the intake manifold replaced on my 3.8L Regal. Since then I found it has not run well. About at week after that the car conitued to stall and the scan showed a failure in the throttle body sensor. We replaced it and th car ran well for about a week. I have noticed a slight vibration on acceleration. Today I could smell coolant, opened the lid and the top of the engine (below the new manifold) was covered in coolant. My mechanic just called and indicated that now the lower intake somethingorother needs to be replaced as well. They are honest and have promised to give me a discount as ‘it should have been done before’. My question is this: is there a chance that failure to do the lower casket may have resulted in damage to the rest of the engine. The car has 240K and up until this problem has never had any major issues. I am hoping to keep the car until it reached 300K, but now I am not sure.

  39. Thank-you for some hope at last!!!
    I cannot open the pictures. Could you please e-mail them to me?
    I sure appreciate your posting this info!! Peace, Mark

  40. Great information…

    I cannot open the pictures. Can you please e-mail them to me?

    Thanks alot,

  41. can i install a series 2 intake manifold on a series 3 motor?

  42. Can you please e-mail pics? Thanks!!!

  43. john sutherland

    i would like to have the instuctions to complete the lower intake gaskets on the 97 bonniville

  44. Does the plastic tube that attaches to upper plenum gasket attach to hole on pressure sensor or just sit open on both ends for recirculating air??? Thanks, Tony, WI.

  45. Jeremy Birkhimer

    i just replaced the lower manifold on my 97 grand prix 3.8 non supercharged and now it is knocking never did this before until i changed out the lower ran for 5 mins and then just died.any ideas as to what could be causing this any help is greatly appreciated.

  46. Could you email me any pictures? Thanks!

  47. THANKS, THANKS, THANKS… You’re the man Joe S. You save us time and money with your advice. YOU’RE THE MAN!!!

  48. Thanks for the info. I’ll be getting started on my monte carlo pretty soon. I thought it was a head gasket. It was leaking a lot of coolant until i replaced the water pump. It didn’t seem to leak at all after that but then broke down 2 weeks later and was hydrolocked like you said at the top of the article.

  49. Could you please email the pictures on how to repair GM 3.8L Intake manifold?

  50. Another important step not mentioned here is to replace or at least clean out the coolant inside the EGR tube which is located on the lower intake. If your lower was completely full of coolant like mine was, there will be fluid in the EGR tube. The instructions that came with my new upper intake say to replace it.

  51. Very helpful article. My daughters 97 pontiac grand prix se has a leak in the upper intake manifold too. Mechanic wants $600 and said its almost all labor. Is there a standard time it should take to change the manifold like the dealers use? I would also like to see the pictures if you could email them. Thank you!

  52. i don’t have step by step pictures but i did take a few while working on my 98 monte carlo so if you are interested in what yours may look like after removing the upper intake, leave a comment on this site or email me @ if u replace the fuel injector o rings, which isn’t a bad idea, you will need a fuel injector nozzle puller. I’ve tried to get them over the lip of the nozzle, trust me, it does not work.

  53. Is an oil change standard with this repair?

  54. Where can I purchase the upgraded intake gasket kit for my ’03 Impala 3.8?

  55. Can you email me the pictures? I can’t open them…Thanks!

  56. Hi my buick lesabre experienced this issue and i want to try and conduct the repair myself but i need the pictures please as they seem to be missing from the webpage, if you could mail them to me that would be awesome. Thanks so much.

  57. I just did this on our 99 Gran Prix. It went OK, just took a long time, but this page had
    some useful information.
    One thing that I found is that you can’t turn over the engine w/o the spark plugs connected and installed – at least it didn’t
    work for me.

    Regarding the tightening sequence, I purchased a new replacement plenum, and the kit included detailed instructions regarding torque sequence, etc, plus a new, smaller diameter passage for the hot air coming from the EGR valve.
    Also, the new plenum actually had the torquing sequence and torque value stamped in the plastic.

    One other thing – make sure you change the engine oil after doing this…

  58. followed your instruction and it went very well. I had water on top of the engine and removed it with paper towels.I removed the plugs and turn the motor over and there was osme water in the cylinders. After replacing the plugs tried to start the car. Now the car wont start. Anything I may have overllooked? thanks

  59. I have a 99 pontiac grand prix gt with the 3.8L. I have had the intake gaskets and upper plenum replaced as well as spark plugs and spark plug wires and a coolant flush. All work has been done at a dealership. When i picked up the car i heard what sounded to me like a lifter tick and after about 10 seconds it went away. Now whenever i start the car in the morning or when engine is cold it ticks for 5 to 10 seconds. What could be the cause for this? I have had the car for 6 years and its never ticked or pinged or anything until i had this service done. Im going to go back to the dealer and see what happens. oh and gas pedal sticks when cold now to. i think accelerator cable needs to be lubed but it didnt do that either until after service has been performed,

  60. Please e-mail the pictures for the upper intake manifold replacement to me, they will not open with the instructions.
    Thanks for your time, Brian

  61. I 2 am having a tapping sound. I’m hoping that goes away after I change the intake. Please Email the pic.s to me also.. vary cool web site. Thanks 4 all your help…

  62. I have had 3 previous pontiac bonneville’s hydrolock (1995 – 1998 models) I purchased a 2001 SSEi thinking that the aluminum manifold with the supercharger would not warp and leak, but now I am losing coolant and have oily foam around the seal on my radiator cap, I called the dealer and they said the gasket still goes out on the SC model. Is the DYI repair proceedure the same as you outline above for the SC model and could you email me the pictures? Thanks so much

  63. Hi
    Excellent article and instructions..very helpful except that I too am unable to open the pics. Is there anyway you can alter your site so that i can open them or can you email them to me? Thanks again

  64. Good article. Want to work on my 97 buick lesabre but could really use the pictures.Cannot open them .Could you e-mail them to me?

  65. followed your instruction and it went very well. I had water on top of the engine and removed it with paper towels.I removed the plugs and turn the motor over and there was osme water in the cylinders. After replacing the plugs tried to start the car. Now the car wont start. Anything I may have overllooked? thanks

  66. 97 pont GP SE with 3.8
    lower intake manifold gasket leaken. Right bihind alternator, never locked but would get hella hot, no smoke no nothang some hesitation everynow and than still ran good. But when i took my upper intake plenum off i had oil sitten in the lower intake manifold. WTF everyone else had anit hmmmm well shes almost ready to go back together i better get back to it thanx. I used a chilton and just tore into the taredone

  67. just wondering if i could have the url for the pictures for this article or maybe you have a pdf format to email me i would appreciate it thank a lot NICK

  68. I own a 1997 Grand Prix GT with the infamous 3800.

    Bought it for 500 bucks from the owner thinking the head gasket was blown, Bought the Dorman Intake, and the FEL-PRO Lower Gaskets, Will have it together tomorrow.

    My situation was that coolant and oil were mixing, and it got up into the throttle body! never hydrolocked, but it was stalling out. I am thoroughly cleaning EVERYTHING as I go. Definetely CHANGE THE OIL!

    I will post an update upon completion.

  69. Please E-mail pictures. Thanks.

  70. As far as running goes, it’s a success! However I will note when you have the LIM removed, look very closely by the pushrods, and just in general. As there can become chunks of clotted oil. That is like a blood clot in a human! (BAD NEWS!)

    I was initially a little worried because it was doing the same thing. So I just let it run and idle for a while to get it to temp, gaskets sealed, had some moisture built up in exhaust. Nothing a little bit of driving out won’t fix!

    Also after the oil change I performed, it’s not 100% clean, but I will change it again in a week or so. I still get a little of the “snotty” looking residual coolant that’s still ending up on the oil cap. The oil from the dipstick now is maintaining a healthy color/smell now.

    And now I can personally endorse this as a fix for this great motor!


  71. Not trying to brag, but I did it without a Chilton/Haynes manual. I just got the torque sequences from forums online and utilized my sharp memory!

  72. I had exactly the same problem today. Pulled the plugs and water/oil came pouring out. After all the plugs were out it turned over fine. I’m not interested in fixing it. The rest of the car is in nice condition. If you want it let me know, or I’ll sell it for scrap to my junk guy.
    Kevin, Orlando FL,

  73. Please send the pictures, I can’t see them. I had the upper intake replaced years ago on my 98 pontiac Bonneville and now it looks like it’s leaking again. But the only place I actually see any water leaking is from a little metal tube coming out from the lower intake. If you look at the engine, standing in front of the car, its to the left side, right below the plastic upper intake. There is a small metal tube coming from the lower intake manifold, right under the plastic one. This pipe goes thru the belt pully tensionor and disappears. I can dry off the tube and see it start leaking. I’m wondering if this tube is my problem and not the plastic intake manifold again. Any Idea? I wish I knew the name of this tube but I tried to descrip it the best I could.

    Thanks for any help and the pictures if you will send them. Robert

  74. The instructions on this page were very useful and helpful. Thanks. However, after I completed the removal of the upper intake and then replaced it with a new NAPA brand upper intake manifold, gasket, EGR chimney, drained the cylinders, new spark plugs and refilled the collant. My 99 Grand Prix started very hard. Finally got it to start and it had a horrible miss and it steamed/smoked for 20 munites. Slowly it began to pick up the missing cylinders and smooth out.

    How the car has a horrible hessitation/lag from idle to any acceleration. After the lag the RPMs pick right up as normal. Has anyone else experienced this problem? If so can you share with me what you found out the problem was. I have let the car idle about 45 minutes total.
    Check ingine light is blinking too. I have yet to scan it.
    Any ideas would be appreciated.
    And yes I have already thought about trading it off. LOL

  75. It is very help. IMy 1999 Buick Lesabra has problem this morning with white smoke and wait for 10 minutes, it can’t start any more. I search internet and find your message is very helpful. But the webpage miss pictures. I will replace the parts by myself. It is cold here Ottawa though (-20C). Hopefully I can get it done. Thanks.

  76. I just replaced my intake and gasket. When I finished I noticed that when the engine is runnig and I try to remove the oil filler cap there is a large amount of suction holding the oil cap on. When I pull the cap off, the motor stalls. What is going on. I have never noticed this before. Is this going to hurt the engine.

  77. I did this in March of 2009 on my brother’s 97 Le Sabre. It was not hard at all, and I didn’t need the pictures. The steps are written out well enough. Make sure all electrical connecters are FIRMLY seated while putting it back together. I pushed the one for the throttle body in but apparently it didn’t ‘click’ in. It wouldn’t start because it wasn’t opening and letting air in. Lucking my brother pushed on it and heard it click. After that it started right up. We changed the oil in it before starting it of course. He changed it again after 500 miles or so.

    For about a day it ran rough with the engine light on. The next day it turned off and was running fine, so don’t freak out, it just needs to clear the coolant/water from the places you didn’t get to. Also the computer takes time to readjust itself.

    You can do it, I promise!


  78. To Craig:

    I would guess the suction is due to the gasket not seating correctly. Also, make sure the replacement stem is seated correctly and all the way in, we had to tap it in with a piece of wooden broom handle and a mallet.


  79. 2001 Buick Regal GS (Supercharged)
    Problems started w/ coolant leaking (intake). Coolant must have loaded up in one of the cylinders and when I took off from a stop and stood into the throttle a bit, I ended up chipping parts of the edge of the top of the piston off and grinding them into/onto the cylinder wall, causing a knocking.
    Motor is out of car on engine stand. Heads/intake off. Hoping to be able to hone cylinder, put new piston in and be good to go. Anyone have any thoughts?

  80. I would really appreciate getting my hands on those pics. If you still have them can you forward them to me. If anyone reading this has them I would appreciate them

  81. Replaced both UIM and LIM on 97 non sc G.P..
    TPS P0121 showed up right away after starting. The car runs great and seemed to be more responsive.
    Replaced TPS, cleared code and it come back. If I hold the gas pedal down slightly while starting the light will not come after its cleared. On the next start up if I dont hold the pedal down the light will reappear.

  82. Jusdt a note to you guys who have posted here:
    1. YES, you do need to change your oil and filter! Even if it hasn’t yet turned to brown sludge, it’s cheap insurance!
    2. Likely the reason it won’t start afterward is because you cheated and did NOT replace the spark plugs. Burned A/F can glaze them and you may even see a weak yellow spark, but trust me on this – try new spark plugs. I’d do it anyway since if you are doing this properly, the plugs are already out and those back 3 are a real pain to change later. Go ahead and remove the strut bar temporariily if it helps, your wheels won’t fall off. Changing your plugs is also far cheaper than all the sensors you will replace that won’t do any good. Make sure there isn’t any more liquid squirting out of your spark plug holes before you put the new ones in. (If you are like most of us, this will take 2 people…one to turn the key and one to watch the engine…)
    3. Save the headache and DO NOT use a plenum from a wrecking yard. You’ll likely be doing this again in the future if you do. In January, 2010, the plenum kit (includes the gaskets & o-rings) from NAPA (part # 600-1186) will cost you about 130 bucks. (I am a shop and that’s what it cost me) From O’Reillys it is about the same. My local Carquest could not find one.
    4. Make sure you don’t have gas leaks at the injectors after you put it all back together. Use the NEW injector o-rings that come with the kit. (Make sure you use the right ones) A pinched o-ring can cause you major headaches. There is no such thing as a little gas fire…

  83. Guys if you installed a new UIM please make sure you put in a new PCV valve as the kit I bought did not come with a PCV valve or it was removed. I had P 108 MAP & P121 throttle position sensor codes set plus higher than normal idle plus some surging.

  84. This might be useful !
    2001 firebird v6 3800. I had a bad coolant leak in the front of the motor.
    While getting prepared to replace the intake manifold gasket , found the leak by accident. The tension pulley assembly has a coolant flow through going to the heater hoses. There was a small crack in the back side of the tension pulley coolant flow through, allowing coolant to run down the front of the motor. This was a very simple repair. Good Luck

  85. I was getting ready to change a thermostat because I thought it was leaking until I found this article. Leak is not bad yet, but I am pretty picky about leaks in general. Good info in this article. I have had very good luck with my ’99 grand prix, upper intake made it 190,000 miles before it went out. Thanks for the info

  86. Getting ready to tear apart my 99 GP SE, due to leak in this area, lot of this info helpful, hope i dont have these starting, seizing up problems u all are talking about. I will leave comment on here Thursday or Friday when hubby gets this done, have to wait to get parts from Omaha NE.

  87. I had a shop do this work because i didn’t know this site existed. my car now has a engine knock around 1200 rpm. Any ideas?

  88. can anyone please e-mail these pictures to me if they have them? Thanks

  89. Good News! I found the series of six videos on this site on a 3800 manifold gasket replacement. I watched all six videos and am very impressed. This is a fairly complicated repair, this video is well done and very clear. Go to “Shop Now” above and then “Instruction & Video” and then

    Or just go directly to and click on instructions & video then type in manifold.
    Good Luck!

  90. Great article

    Can you please email me pictures to

    thank you for your help


  91. Can u please email me the pics, thanx

  92. can u please email me the pics,

  93. Just had the intake gasket replaced today on a 96 Grand Prix due to the common coolant leak. However, after driving it for the rest of the night the car died and needed to be jumped. the lights dimmed and battery light came on as if alternator wasn’t working. My guess is the shop didn’t hook the alternator back up correctly and dont think the alternator is bad. It’s difficult to find and follow the wires but seems everything is connected. Any ideas why the car is running from the battery and not the alternator?

  94. About 7 days ago had complete flooding from Plenum into engine on a 98 Park Avenue with no turbo. Had the intake manifold gaskets replaced, valve cover gaskets and new plenum. Oil has been changed 3 times making sure all coolant is out. Car starts great, no cololant loss in 7 days, runs great, temperature excellent. All is good except during warm-up we get white smoke. Again, there is no coolant loss, and no real smeel to the smoke, it just seems like vapor. After 3 to 4 minutes as the car warms up the white smoke goes away. Any thoughts on this would be appreciatted.

    As for those who said that had a knocking after the replacing the above, I had the loud knocking also. The mech and I both believe it is lifter noise. We drained the oil, added a quart of Marvel Mystery Oil and the rest new oil. After starting the car, noise lasted for 21 seconds then went away and has not returned. I plan to do another oil change in 30 days and add another quart of Marvel. We both believe the sludge of old oil/whatever was makin the lifters stick and the Marvel unstuk it.


  95. Is there a way you can email me these instructions? I don’t see the pictures.


  96. Is there a way you can email me these instructions? I don’t see the pictures.


  97. I got one for ya. I have a 2002 3.8L non-supercharged engine that I replaced the upper intake plenum and gasket. After torquing everything evenly and through three steps I seem to have a leak, but not for the coolant. it it creating a sucktion through the crankcase. I hear a squeeling noise when at idle, but at higher RPM’s everythring disappears. When pulling the oil fill neck off you can really feel the suction. When the oil neck is removed the engine chugs or lopes and the squeel also disappears, then comes back when it is reinstalled. Any I deas? I have heard of blow by but never a suction like this.

  98. Just finished this on my ’98 Bonneville; works great. The Dorman manifold was in stock at my local auto parts supplier and sells for $129. My car was not yet severe and did not hydrolock, but it had the characteristic flood of coolant on top of the lower manifold.

    Things to note:

    – Double, triple check that every electrical connector and vacuum line you unplug is reattached when you assemble. Those of you who say the car does not start–chances are you’ve missed an electrical connector or did not seat it fully. Those of you who say the car runs rough–check all vacuum lines including the master cylinder.

    – The Dorman kit includes a replacement EGR riser; make sure you install this securely. Mine was a loose fit. I knurled it by hand and applied loctite compound. I seated it by placing a small piece of wood on top the riser and gently driving it downwards with a hammer.

    I changed the spark plugs as directed on this site. The old plugs did not appear damaged although some were slightly fouled. I turned the motor over with the plugs removed–no visible liquid was ejected from the cylinders. I completed this procedure before I reinstalled the alternator, since the rear spark plugs are difficult to reach in my Bonneville.

    My oil level was above the “Full” mark, indicating that some mixture had likely seeped into the crankcase. I changed my oil and filter–it’s rather silly not to once you’ve gone to the trouble to change a manifold.

    Good luck to everyone else who needs this repair. It’s not difficult and can be completed in an afternoon, but make sure you take your time cleaning the gasket surfaces, torquing the bolts properly and checking all the electrical and vacuum connectors.

  99. Jake, in your case I would double-check that the PCV valve was replaced and correctly installed during this procedure. The Dorman kit includes a replacement PCV valve. You will find it at the far end of the manifold opposite the throttle body.

    The PCV valve is easy to access with the engine cover removed. The assembly includes a sensor with wire harness, the valve, a spring and a pair of O-rings. If any of these are missing, a vacuum leak may result.

  100. INTAKE BACKFIRE! blew the manifold into 3 pieces jus pickd up the car for short $ 2001 grand prix gt. was troing to start and kaboom!! the explosion knocked off a fuel line which im thinking cause the small fire.So i have it all stripped down and ready to reinsatll new manifold,but what caused this backfire ,i think i should be fixing this first . im told a relay,mass airflow sensor.ignition something,timing,ummmmm help! by the way ive never seen an air filter as dirty as this one never changed?! part of cause?

  101. can anyone tell me which way the white or clear tube with a bend on one end is for, and which way it is supposed to be facing? When I took the old plenum off the white the bend in the tube was toward the passenger side of the car. The new plenum the bend in the tube was towards the driver side of the vehicle. Oh, It is a 1997 Buick park ave. by the way !!! thanks !

  102. could you email me the pics. Thanks

  103. Can you email me the pics. Thanks

  104. Hello.
    I am a 19 yr old pregnant woman.
    I replaced the upper plenum in a 1995 Buick Park Avenue all without pictures or any directions. I found this site AFTER I did my replacement, but this site was very helpful in letting me know I did eveything correctly.

  105. My husband is currently working on an 2003 Monte Carlo SS. It was leaking coolant. He replaced the upper plastic intake. Put it all back together. Car starts and idles good. Accerlation the car sounds awful. Engine makes weird noises. Any advice?? PLEASE HELP!

  106. Pontiac Grand Prix 1998 was losing coolant, low coolant light stayed on but the car would have coolant. Ran hot one morning and had white smoke coming out from under the hood. Replaced water pump and low coolant sensor. Hasn’t ran hot, but still has white smoke coming out from under the hood on passanger side when setting still. Is this a sign of blown head gasket? Please help.

  107. what is normal operating temperature for these engines?–my daughters olds 88 running at 205-210…..seems hot to me

  108. I would love to see the photographs, but they are missing. Used IE 6 & IE 7 on both Windows 2000 and XP. Can’t see them in any situation.

    Hope you can fix it soon.


  109. Looking at a ’99 LeSabre to buy. Is there any way of knowing if the intake has already been done. The car has 90k miles and looks and sounds great but the person selling it doesn’t know if the Intake was ever repaired. Also does the problem always happen or just on some vehicles? Thank you and thank you for the excelent info. Steve

  110. Just did this repair. Had to replace the upper plenum because the edges around the Orings were broken. Cost $154 and change through Oreilly Auto Parts. Took about 5 hours. Could do it again in 2 hours now that I know what I’m doing. I was leaking about 4 ounces a minute, but it was all going outside the engine. No signs of dampness inside the engine. Took the plenum off with the throttle body intact. Seemed easier that way.

  111. One note:

    If you buy the 3 piece gasket kit, DO NOT remove the throttle body as those gaskets are not included in a 3 piece kit. A new plenum should have all the gaskets already installed in it.

    The above instructions weren’t perfect to my vehicle (95 Regal 3800), but were close enough to make the job easy. There’s no reason why a person with reasonable backyard skills can’t make this repair. I suspect many cars went to the junkyard instead of making this simple repair. It’s easy to think it’s a cracked head or other serious problem.

  112. My 1999 Olds Intrigue is back on the road. The part from autopartsdirecttoyou was a lot better priced than the same manifold anywhere here in Canada, even after shipping and the rest of the fees. Dealer wanted almost 1500.00 to do the job I did for under 200.00 My hat is off to you gentlemen the part and instructions were second to none.

  113. Changed plenum and gaskets on 99 lesabre. The instructions were dead-on. Once I was done, installed new spark plugs and it started right up. It knocked for about a minute and smoked for about 10 minutes. I tried to absorb all the antifreeze i could from the intake, but what i couldn’t just got burned off. I’d recommend buying a new plenum, like Keith said, mine came with all the gaskets, o-rings for the fuel injectors, plus a new pcv valve. Thanks

  114. Please email pictures

    Thanks for the info. I just purchased a really nice 96 Firebird. Seller gave me the quotes for repairing the “head gasket”. $4500.00! I think this intake repair will do the trick. My daughter is going to help fix “her” car. Please send the pics. Thanks!

  115. u r smart as hell about the elbow tube thanks a million dude

  116. There are no pictures showing up on this website. how can I get the pictures so i can see exactly what you are explaining.

  117. The instructions that were given were to the point. It took me no time to complete the job. Excellent explanation and directions overall on how to remove and replace the intake manifold. You intervention saved me a ton of money.

    Thanks for the help.

  118. This is a re-post from back at the beginning of 2010, with some extra info after reading some of the newer comments…

    I did this in March of 2009 on my brother’s 97 Le Sabre. It was not hard at all, and I didn’t need the pictures. The steps are written out well enough. Make sure all electrical connecters are FIRMLY seated while putting it back together. I pushed the one for the throttle body in but apparently it didn’t ‘click’ in. It wouldn’t start because it wasn’t opening and letting air in. Lucking my brother pushed on it and heard it click. After that it started right up. We changed the oil in it before starting it of course. He changed it again after 500 miles or so.

    For about a day it ran rough with the engine light on. The next day it turned off and was running fine, so don’t freak out, it just needs to clear the coolant/water from the places you didn’t get to. Also the computer takes time to readjust itself.

    Tip Edit: For the People getting coolant in their engine AFTER changing… You probably did not install the stem right, and no, do not indent it with a chisel. It fits tightly.. I ‘popped’ it in rather easily.

    Using an old wooden broom handle end (wood cylinder), I placed it on top of the stem/tube then tapped it a few times, firmly with a rubber mallet… of course I did this AFTER assuring a few times of it’s proper alignment. it should seat in solidly.

    To the fellow that had the problem with the car cranking fine, and getting spark/gas and everything but not starting… Take heed to the information about the problem I ran into with the electrical connector on the throttle body… it may not be getting air. Recheck ALL of your electrical connections and make sure they are tight and locked all the way into position.

    Another leak point mentioned earlier is the plastic elbow that comes from the lower manifold on the passengers side. This leak is hard to find, and I had this trouble on my Regal, years before changing the upper plenum on my brother’s car, This involves removing the serpentine belt, the alternator, and the belt tensioner. (Coolant runs in and out of a manifold in the backside of the belt tensioner, Pop the elbow out, making sure the orange ring is there, you will probably notice it is deteriorating and also the plastic is deteriorating on the end. If you have any pieces missing, use a flash light and long tweezers or something to get that crap out of there.. Be careful not to knock it in, be patient, I had this problem. Replace and put back together as it came apart.

    That’s about all I can think of for now guys, good luck. And thanks again to the person who wrote this, as I’m about to do it again on my Regal with 244,000 mi. on it. If anything else comes to mind, or problems/solutions, I’ll post back here. This helped me out a ton, and I’m trying to ‘pay it forward’ a little by giving a few helpful tips.


    You can do it, I promise!


  119. Ok guys. Finished the UIM on my regal. The dorman kit instructions warns to make sure all the o rings are installed correctly on the new PFC valve and supplied fitting or else “whistling at idle, oil in the manifold, high idle, rough running and vacuum in the crankcase will occur”. That , more than likely, explains the suction problem some were having. Be sure to replace the lower intake manifold gasket as well, and get the aluminum backed one or at least the one with steel reinforced mounting holes. I didn’t replace the LIM gasket on mine OR my brother’s and I think this was a mistake since you’re already pretty much there once you remove your old UIM. He recently has seen the coolant in the oil cap and I suspect that this is from the LIM gasket leaking. I will tear mine back down and do the gasket. I will also post more tips and try to photo bucket link some pics for you guys during the process from start to finish, although you won’t really need the pics. I found that after doing my brother’s UIM/Gasket that I didn’t even use these instructions to do mine. It’s really not that bad of a job and took me about 3 1/2 to 4 hours for the UIM Replacement procedures. I’ll post back later with updates.

  120. i am currently doing my UIM and i am stuck i cant seem to take it off question is how many bolts are holding it down n would sealant cause it to be because it seems the previous owner use gasket sealant n i wasnt able to see the pics on here if u would please be able to send them to my email … for any help guys appreciate it

  121. Great information. Is there anything that I need to know when attempting to do this on my 2001 Lesabre that has not been mentioned yet? Pictures would be helpful if anyone still has them. kc7cnc@gmail.

  122. dude! thanks for this information. i thought it would be strange googling “how to replace intake gaskets in my monte carlo” but it paid off. my sister scoffed, i held my head though and followed these directions. i had a coolant leak for months, and i got tired of spending $ on dexcool every week, so i finally broke down to do this.

    i am a very novice auto mechanic, tearing into the engine scared me because i only have one car, and cant afford another. but these instructions were very very very helpful. i replaced upper and lower gaskets, all together it took me 6 hours and $150 bucks. much better than the week and $1400 i was quoted. my back hurts though, ha.

    thanks again for being a helpful, money saving savior. 😉

  123. Adrian Oliver

    Thanks for the info i am going tho the same thing loseing collant and i found out it was the upper intake i was reading some of peoples things is it smart to relpace the lower also and if the engine goes into a hydo- lock can u just replace the uper and lower intake and motor be fine again

  124. Hello everyone! I just read some of the comments and I have the same problem on my 2002 Bonneville SLE. I was going to trade my car in for something else but after reading how to do this I figured I can do this instead of paying $2000 or trading my car.
    HERE IS A VIDEO LOOK!!!! Here is a video that someone posted on here on how to replace the upper intake and lower intake on a 3800 series engine on a 1995 Buick Lesabre. The engine concept is the same in my opinion so take a look before making a decision on replacing your manifold on your own. There is 6 parts to the video and look on the left side for the other videos scroll all the way for the other part series and you should be good.

  125. Sorry, I said look on the left side for the videos it’s on the right hand sides.

    “There is 6 parts to the video and look on the left side for the other videos scroll all the way for the other part series and you should be good. “

  126. Will this repair also work on my 2000 camaro 3.8 liter v6 (series II)

  127. Jeff, I have a 2001 Camaro, same 3.8 liter. I used these instructions kindof as a general guideline, but with the rear-wheel drive setup, a few things are different. I had never done this before but i didn’t find it very difficult. also, while i had the upper intake manifold (plenum) off, i went ahead and took off the lower to replace that gasket too. Only advice I can give you is to mark where every bolt goes: one bolt had me stumped for a day and a half before i figured out it went on the front of the distributer cap, (which i had to loosen, but not completely remove.) ANYWAY, yes these instructions are pretty useful, but you can’t follow them perfectly. Also, you’ll need a special tool to remove the fuel lines, cost 8 bucks at autozone. if you have any sepecific questions, you can emial me at and i’ll try to help you out. I litterally just did this in the last week or so. Good luck, it’s a good engine!

  128. can you send me the pictures Thanks!!

  129. 1997 Old 88 3.8 series II with 51k. You saved me alot of work. Thank you. Thought I had blown head gasket. When I removed the intake rubber, in front of the throttle body, it was full of antifreeze. I found your instructions through google. Fairly easy job. I did the oil change and sparkplugs but didn.t pull the lower intake. Runs great again. I also recommend pulling and reinstalling the fuel rails and injectors together, put oil on the new o-rings you install on the lower injectors.

  130. Charles Wallace

    Some ideas for disassembly and reassembly of your car

    Before taking things apart, use a camera to take pictures of the parts of the vehicle that you plan to disassemble. Close ups of the way things fit together can help one remember what it looks like assembled. There may be delays getting parts or for other reasons and it is easy to forget the details of how you took it apart. All electrical connectors need to be identified by a numbering system on each part of a pair of connectors with notes taken at the time of disassembly as to what goes where. The same goes for fuel and vacuum lines.
    When reassembling the parts, if you have seven of eight connectors accounted for, you have forgotten one of them! Your step by step take apart list helps to keep this from happening.

    Before starting disassembly, clean debris from the engine, especially in sumps around spark plugs, which if not cleaned might invite debris to fall into the combustion chambers. Once you have parts removed, clean them as you make note where they are to be replaced when you put the engine back together. Bolts can have their threads chased by using a die of the right size. Threaded holes can be cleaned by using a tap to chase the threads.

    Cleanliness is perhaps even more important in the valley under the lower intake manifold of a GM 3800, for example, should you decide to change it’s gaskets. The lifter assemblies are open to contamination from old caked oil deposits around the push rods and associated parts, which if entering a lifter is likely to cause a loud clicking when the engine is restarted. A lifter can be blocked from normal operation due to crud getting into it from the oil which got contaminated.

    Fasteners (bolts and nuts, etc.)
    There are specific lengths of bolts when an assembly is taken apart. For example, upper plenum bolts on a GM 3800 II are different than lower manifold bolts and some of them are longer than the rest. Make a quick note of where the long ones go, and of the possibility that some might have a an integral stud on the one end. Keep bolts for one assembly separate from the others in some sort of reliable holding device. I like to use plastic ‘clam shell’ boxes which originally held muffins since there are multiple pockets to put thing in, and the containers are transparent so things don’t hide. Since one is working on different places under the hood, parts associated with a throttle body for example could be kept on the cowl near the driver’s side of the car while alternator items could be on the passenger side near where it is mounted on the engine.

    Order of operations
    There is usually a definite order of disassembly/reassembly. If you have manuals for working on the car, read the steps given in the manual and use these to make your own step by step set of take apart instructions. Write the steps up on your computer and take notes in blank spaces between lines for specific details while taking things apart. The manuals usually are very terse and lack small details which you encounter while taking things apart. Reassembly will consist of putting the thing back together in roughly the reverse order of disassembly. You might go back to the computer and write step by step reassembly instruction by working backwards from your disassembly instructions.

    Keeping track of items
    If the work area is open and well organized, placing parts on clean table tops and shelves helps to keep the work organized so as to avoid losing track of where you put something. Items should be easy to see where they are placed so as to remind you where you put things.

    When talking to fellow ‘amateur’ mechanics, I sometimes hear something like this. “I’m going to Tear into the Buick this afternoon”. This means that the disassembly will be done by looking at the job and going at it. This is OK if the job is small and can be done before one forgets what went where. As this mechanic gets on in years, like 40, the ability to do mechanical work this way begins to encounter problems. I noticed this when doing the minor job of cleaning off corrosion and then repainting the plate under the battery on my 1991 Blazer. I got it out OK but when putting it back together, I first forgot the battery hold down bolt. I took the plate out and put it up from below the plate where it was supposed to be and then put the plate back in. This time I noticed that I had the black ground wire on the wrong side of the plate. It took three times to get the plate back in properly. So it went. I was beginning to think that I had better give up doing my own mechanical work. I had recently bought a 1999 Buick Park Avenue, which when studying the posts on the Internet, decided that I had better look to the intake manifold issues. With this in mind, I decided that I would document each step of disassembly by following a written list of detailed step by step instructions. I used my factory manuals and a Chilton manual and made my step by step take apart sheet. The step by step sheets had space between lines for writing details between steps as something I hadn’t had in the instructions would show up while I was doing the disassembly. I made another with the steps reversed for reassembly. I’m glad to say that I have confidence again as I got the whole job done of doing both upper and lower intake manifolds with out error. I had to make one small adjustment. I had apparently used a short bolt where there should have been a long one. I had a lone bolt left when finally replacing the bracket for the EFEVAP solenoid, and it was too long. The short bolt belonged here!

  131. Charles Wallace

    Lower intake manifold replacement
    Thoroughly clean the manifold with degreaser and remove all traces of oil or coolant. A dirty surface invites a leak later. The mating surfaces of the manifold and block must be completely free of old gasket material and debris. Be careful not to gouge the precision mating surfaces of the manifold and block. Wipe the mating surfaces with acetone or mineral spirits to the assure that the surfaces are clean and dry before continuing. Trial fit the gaskets to see how they are to be positioned before doing any actual installation. Use a 3/8-18 tap and die to chase the threads of the twelve mounting bolts and corresponding holes in the block. Clean the thread debris away from the surfaces. Note, the holes in the block do not make the usual ninety degrees with the block so do not try to force the tap to go vertical into the block threaded holes.

    1. Apply gasket compound sparingly to the traces on both sides of the two side gaskets.

    2. Apply gasket compound to the end block horizontal surfaces where the straight gaskets are to be positioned.

    3. Place the two straight gaskets in position with a dab of gasket compound at their two ends where they will intersect the side gaskets. Their alignment tabs will seat into the holes in the block to correctly align the two straight gaskets.

    4. Position the side gaskets with their alignment tabs into the alignment holes in the manifold. These are on the bottom of the gaskets. Put a dab of gasket compound at each end of the straight gaskets on top of the gaskets.

    5. Lower the manifold carefully down onto the valley of the block with care taken that no gaskets slip out of position. Check with a bright light to see if both ends of the straight gaskets have remained properly positioned. If in doubt, remove the manifold and try again.

    6. One by one, apply thread locking gel to the end of each mounting bolt and place them into their correct holes in the manifold.

    7. Using a 3/8″ socket and extension, snug each bolt down . This must be done in correct sequence to assure manifold seating evenly onto the valley of the engine block.

    8. Using a standard socket wrench handle and extension, start tightening each bolt to a low torque, about 3 Ft Lbs. This may be a feel process as most torque wrenches do no register below 10 Ft Lbs. This is not critical just be sure it is the same for all twelve bolts in sequence. Final torque will be only 11 Ft Lbs, a very low torque. Be careful using the torque wrench. It is difficult to hear the click of some of these cheaper wrenches, especially for such low torque values.

    Sequence is as follows:
    11 1 3 10
    5 8

    6 7
    12 4 2 9

    Note: bolts 5 and 7 are reached in the deep sumps in the manifold.

    9. Continue step 8. while each time raising the torque by a few Ft Lbs. Again be sure to give each bolt the same torque. When you near eleven foot lbs (11 Ft Lbs) for all twelve bolts, use a torque wrench to tighten each bolt in sequence to 11 Ft Lbs. If time permits, wait about 30 minutes and go back and verify the torque of each bolt. This allows for final settling of the manifold onto the gaskets and the block and a possibly finding a missed bolt. Too long a wait will nullify the thread locking compound. When in doubt, go back and start the whole process over again.

    10 Replace the alternator extension bracket with the Torx bolt in the middle of the bracket and the bolt at the driver’s end of the bracket.

    11. Seat the new smaller stove pipe in the kit into the EGR hole in the top of the manifold. Use a deep socket as a driving tool and apply gentle taps through a wooden block to seat it into position. Replace the EGR pipe from the EGR solenoid with the two mounting bolts tightened to about 15 Ft Lbs.

    12. Replace the belt tensioner assembly onto the block. Use a new plastic elbow with it positioned from the tensioner assembly into the passenger’s side coolant port in the head. Apply gasket compound or silicon grease to assure elbow’s end’s smooth entrance into the head and tensioner assembly. Replace the other plastic elbow into the tensioner assembly. Replace the two metal hose adapters into the associated coolant ports. Replace their mounting bolts. Use new O rings and compound to assure a secure leak proof joint.

    13. Carefully align the three 15 mm bolts and holes and tighten the assembly into position. One of these bolts is hard to see!

    14. Before replacing the alternator, replace the three rear (right) spark plugs.

    15. If replacing the rocker covers gaskets, do this also before replacing the alternator in position.

    16. Replace the alternator. Re-connect the single heavy wire with it’s boot to the electrical stud on the back of the alternator and plug the alternator’s electrical connector back in. On all electrical connectors, be certain to push the two parts together firmly until the tabs click indicating the connector is properly connected. Failure in this simple step will likely result in sensor codes and even a non operating engine. Push until it clicks!

    17. Using a breaker bar and a 15 mm socket, overcome the spring in the tensioner and slip the belt back into position.

    18. Put the thermostat and cover back in place and reconnect the upper radiator hose. Use a new gasket.

  132. Charles Wallace

    Upper intake manifold removal procedure

    1. Disconnect negative battery lead. 8 mm box end wrench
    Remove air intake rubber boot.

    2. Mark with felt tip pen all electrical connectors, both parts as follows:
    1- PCV, 2- Bundle with blue lock: release captive peg,
    3- EVAP, 4,5,6 at Throttle body,7-EGR, 8-air intake plenum, 9- Foil wrapped water temperature sensor connector. Separate electrical connectors. Carefully pry locking tab up to clear locking tab in mating connector body, and pull each connector apart.

    3. Mark coils ends of rear spark plug wires 2,4,6 and pull them out of their respective coil assembly, then fish wires under lines on top of manifold and leave hanging near firewall. Leave on rear plugs.

    4. Remove vacuum connections from EFEVAP solenoid valve-
    lines go from 1- throttle body (large push on), 2- fuel pressure regulator-(small 90 degree fitting) and 3-large black (locking). Lines are in three integral sections and can be removed and laid aside. Release lock on white sleeve fitting and pull off the solenoid body. This line passes to rear of engine.

    5. Disconnect the two fuel lines, return and supply. Press the bottom ring which is light in color while first pushing down on fitting slightly and then when the locking ring is depressed, pull off the connector from the rail. Fingers or a small pliers work OK to depress the light colored ring on the bottom of the connector. Release the black routing block which holds the three plastic covered lines. There is a locking tab. Lift lines out of the way.

    6. Disconnect the leads going to each injector. Press in on the wire retainer up hard on the middle of the bail and right against the body of the connector to free the connector from the injector. Place harness and integral connectors out of the way.

    7. Loosen and take off the four 10 mm nuts fastening the fuel rail.

    8. Remove the fuel rail by carefully pulling rail upward while gently rocking it back and fourth evenly on both sides. The injectors will slowly slide up out of the intake manifold. Lay assembly aside.

    9. Remove ERG heat shield- a 10 mm bolt and a 10 mm nut hold it in place.

    10. Remove the throttle bracket nut

    11. Pull the plastic manifold vacuum body out of the plenum. Two tabs will release it. This is on the rear of the plenum in the center.

    12. Remove nuts (3) holding throttle body to manifold- Push the bracket on the left side of the throttle body to the left to gain access to the bottom left nut. Remove throttle body and lay it and attached cables on the cowl, out of the way.

    13. Remove the manifold mounting bolts (10) Note where the four long bolts are used. Two have a stud on top (left rear driver’s side and front right passenger’s side) .

    14. Remove the upper manifold. Do not pry as the manifold will come off with out forcing. If it is tightly in place, a mounting nut has been missed.

    15. Cable harnesses can be pushed aside and over the top of the throttle body end of the plenum to make removal of the plenum easier.

  133. Charles Wallace

    Upper manifold replacement procedures

    The lower manifold top surface needs to be thoroughly cleaned on it’s machined gasket mating surfaces. When the plenum is off, be extra careful to avoid debris getting into the intake ports. Small soft lint free rags can be effective in blocking these four ports. A shop vac is useful in extracting debris which may have gotten into the ports as work is being done. There may be engine oil on the top of the lower manifold due to seepage up the ten head bolts. This could indicate that the lower manifold gaskets are failing. The lower gaskets are simple to replace at this time if necessary, but it doubles the cost of the job and requires remembering all of the steps for both jobs if it to be done. On my job, I was reluctant to go the extra distance, but am glad I did. There was old thick oil in the two deep sumps where the hidden bolts for the lower manifold are located and a thick coating of oil everywhere else. I decided to do both manifolds and in the process of replacing the sparks plugs on the rear of the engine, I found plug #4 very loose. Since the plugs apparently had not been replaced at 100,000 miles, this was not an unexpected outcome. The engine has more power now, not unlike my 97 Riviera. The lower gasket was a worn, leaking and a crumbling looking disaster waiting to happen!

    1. Separate the new gasket from the plenum. Apply sealant/adhesive as needed to help keep gasket sealed. Sealant should not be applied in excess. Just a light smear on the traces of both sides of the gasket is enough. Sealant is not always recommended, it is a matter of opinion I guess. Since there may be warping even on the new plenum, the sealant might go a long way to prevent leaks later. Replace the gasket over the guide posts which align the gasket with the plenum.

    2. Place upper manifold (plenum) onto lower intake manifold flat surface. Two alignment posts in plenum assure proper positioning of plenum onto the lower manifold holes.

    3. Install manifold bolts (10)- There are four long bolts, two with stud top (left rear and front right). Torque to 4 Ft Lbs.

    4. Tighten (10 NM) in sequence as follows:

    5 1 3
    9 7

    10 8
    6 2 4

    Start by tightening the bolts down finger tight. Then use an 8 mm socket and a extension handle to tighten each bolt in sequence, one at a time, around the sequence four times, gradually increasing the torque each time until arriving at about 4 Lb Ft. You will feel a definite stop to the bolts’ rotation when you reach this level of torque. Do not over torque these bolts as the plastic body of the plenum does not tolerate excessive torque.

    5. Re-install throttle body and support bracket using three 10 mm nuts and place throttle body bracket back in position and replace it’s fastening 10 mm bolt. You may want to leave the three nuts loose until the bracket hole aligns with the shield’s tapped hole. Tighten to spec.

    6. Push kit provided plastic manifold vacuum assembly back into port on rear center on upper manifold. Block the small port as it is not used. A short piece of tubing with a small bolt for a plug works OK. Use new ‘O’ rings and compound to assure a tight vacuum seal.

    7. Install cable bracket to head mounting bolt.

    8. Install EGR heat shield using one 10 mm nut and one 10 mm bolt. Shield fastens to the studded manifold (right front) with a 10 mm nut and has a 10 mm bolt fastening it to the alternator extension bracket. It makes a roughly clockwise one third wrap around the solenoid, with the straight section of the shield on the left of the solenoid, parallel to the firewall.

    9. Install fuel rail. Put small amount of silicon grease on each injector’s newly installed ‘O’ rings. Put silicon grease around the convex opening in lower manifold for each injector. Carefully lower rail and injectors back onto the lower manifold being careful that each of the injectors smoothly and fully enters the lower manifold. Re- install the four mounting bolts.

    The new ‘O’ rings for the injectors are replaced as follows. First, use a knife to run around the metal rim edges and break the ‘O’ ring away from the metal rims. Do this on both sides of the old ‘O’ ring. This loosens the ring. Next, use the tip of a small knife to push tip into and perpendicular to the body of the end of the injector, between the ‘O’ ring and the outer edge of the ‘O’ rim groove. The old ring can now be lifted slightly to get the tip of the knife under the ring and lift is away from the body of the tip of the injector. The ring can now be removed completely. Put silicon grease in the groove of the tip and work a new ‘O’ ring over the end of the injector and into the groove. Feel that the ring rotates freely in the groove under your fingers. Do not try to dismantle the injector’s ‘O’ ring metal groove.

    10. Replace injector electrical connectors- assure locking bails are in place. Reposition the cable harness back to its original position around and on top of the upper plenum.

    11. Take a time out to check all of the presiding steps to assure nothing so far has been overlooked.

    12. Reconnect the two locking plastic covered fuel lines. Supply and return. Position these lines in the support block on the cowl and on the EGR shield bracket plastic triple block. These lines are critical for safety. They should not be nicked or bent or otherwise abused. Gasoline leaks are not fun. The third line is a vacuum line to the cabin.

    13. Reinstall the EVAP solenoid mounting bracket with its Torx bolt. Reinstall the EVAP solenoid.

    14. Reinstall the vacuum lines on the solenoid. 1. Throttle body line- large push on, 2. fuel pressure regulator line : 90 degree push on, 3- large black locking line, 4- large white locking line to cabin.

    15. Reroute and reconnect rear spark plug wires- 2, 4, 6 onto coil terminals- top 6, middle 2, and bottom 4

    16. Reconnect the electrical connectors: 1- PCV (with new PCV valve and
    ‘O’ rings installed), 2- Cable bundle with blue locking tab, 3- EVAP solenoid, Throttle body lines- 4,5,6,7, 8-Air intake temperature, 9- Coolant temperature sensor (foil wrapped). With all of these connectors, be certain to fully seat connector with enough force to hear a definite click when the connector halves are properly seated.

    17. Replace air intake boot on throttle body.

    18. Replace air filter assembly.

    19. Reconnect negative battery cable using 8 mm wrench. Be careful not to let wrench touch positive battery terminal.

    20. Before restarting the engine the first time, close the radiator drain using a 3/4 inch socket and extension handle. Put silicon grease on the plug before reinstalling it. Do not use excessive torque on the plug. Refill DEX coolant mixture 50%/50% using distilled or reverse osmosis water. It takes time for the system to purge air from the passages and hoses so take your time. When the radiator seems to be full, turn on the heater to max, start engine and keep close watch on the level in the radiator. When thermostat opens and water is circulating, trapped air may cause coolant to spill from filler, but system is not full yet. It will likely need to be topped up several times until the radiator is full and water can be seen circulating freely in the radiator. When system is stable, replace radiator cap. (New one?) The coolant recovery tank can be topped up with the same mixture.

    21. All presets on the radio will need to be reset. The custom settings system for the seats, etc., will have issues as well and may need a trip to a Buick dealer to reset the computer to allow the system to work again.

    22. The fuel gage may be no op due to a power surge from the computer when the battery is again re-connected. This may be due to the gage’s pointer being stuck behind (lower than) the empty pin of the gage, but by using a small but powerful magnet, may be possible to rotate the magnet over the pointer, remotely turning the pointed backwards. By turning the pointer all the way counter clock wise as you rotate the magnet hard up against the lens, you may be able to bring the pointer back around to empty on the other side of the empty pin where it belongs.

    23. For the next few days, monitor the radiator coolant level. The coolant recovery tank should take care of this over several days’ use of the car. There may have still been air in the system which is eliminated as the engine goes through several cool to hot sequences and the air bubbles out into the coolant recovery tank as the coolant temperature rises. When the engine cools, coolant is siphoned back into the radiator, replacing the air which was still in the system.

    24. Coolant leaks may be due to various factors which show up after the job seems to be done. If you find coolant under the vehicle, study the place up on the engine above where the spot is on the ground under the car. Leaks might come from the two plastic 90 degree adapters in the alternator mounting bracket, the two metal heater hose adapters, the upper plenum of the intake manifold, and unlikely from the lower intake manifold. The coolant can drip from an hidden location on the engine and be carried around under the engine to the place above the ground spot where the leak appears. Heater hoses may leak as they have been disturbed during work on the manifolds. It might be necessary to re- torque the plenum mounting bolts, for example. Some small seeps seem to resolve themselves as the engine parts heat and cool over a few day’s use with the expansion bringing the gaskets more firmly into play.

    25. The computer may need a few miles to relearn the many parameters which it monitors during running of the vehicle. If the engine seems generally OK but not like it did before the work was done on the engine, it may be that the relearning will correct the issues.

  134. Charles Wallace

    Lower intake manifold removal

    1. Remove upper intake manifold

    2. Drain coolant

    3. Remove upper radiator hose and thermostat housing.

    4. Remove the alternator held by four bolts and diagonal bracket. Disconnect electrical connections.

    5. Remove belt. Remove drive belt tensioner. This is quite a task since it is held in place by three 15 mm bolts and three coolant fittings which are difficult to disengage. The plastic parts should likely be replaced while the tensioner is out.

    6. Remove EGR valve outlet pipe. Use a puller to extract the stove pipe part of the ERG system. This will be replaced with a smaller tube to prevent UIM gasket damage.

    7. Remove generator bracket extension which is held in place by a Torx bolt
    and a second bolt on driver’s end of bracket.

    8. Remove lower manifold mounting bolts including the two deep in the sump pockets on each end of the manifold.

    9. Remove lower intake manifold by temporarily placing four nuts on the studs on the front and rear top of the manifold and using a small pry bar to apply lifting force to the manifold. Do not damage the surfaces of the manifold or the block by prying between the mating surfaces.

    10. Lift the manifold up and out being careful to keep the gaskets in some sort of order. Look at the mating surfaces and gasket condition to assay possible causes issues found with the engine. Bolt holes for example leak oil up on top of the lower manifold. The newer gaskets will correct this problem.

  135. Charles Wallace

    I ordered the replacement gaskets from AutoPartsDirect and they came in less than a week. The total cost for the project was $188 for the gaskets and $25 for the elboes from the dealer. The project took about two days and except for a minor leak of coolant at first and the crazy fuel gage, there were no other issues. The coolant leak was corrected by tightening the upper manifold bolts on the throttle body end of the plenum.
    Thanks to all who posted their ideas and experiences. This is a great service toothers!
    Chas W.

  136. HELP! Need pictures! Please email to

    My daughter’s 97 Buick LeSabre’s motor seized up when the mechanic shop did a diagnostic test to see where the coolant was all disappearing–and engine overheating. Said the motor was fried. Now we have hope. Taking it to a mechanic friend with your info. Thanks so much.

    Linda H

  137. Where can I find the pictures or if someone can send them to me, thanks

  138. this has been very helpful, for fear of not having worked with EFI before , ive known for some time i couldnt use coolant as my cat got clogged and o2 sensor reads an error , and of course i own a 2002 implala ls. i have faith i kn ow what do thanks video and wriiten input both put me at ease and confident thanks a million

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