intake manifold gasket procedure?

Hello and Thanks in advance for any input. I have a 1999 Grand Prix 3800 engine with 105000 miles.Recently I noticed antifreeze getting low quickly.About a gallon every 2-3 weeks. As far as I can see there is no external leaks. Car fires right up everyday and runs like new. Very little coolant in oil. I guess its burning off in the combustion chambers or leaking out the exhaust ports? So I plan to do the upper and lower intake manifold gaskets to hopefully fix the coolant disappearing and avoid major engine failure. I looked for a repair procedure in tips and maintenance but couldnt find any. So my questions are... should i replace the plenum or reuse the original? Should I go ahead and do the head gaskets as well while its all apart? And obviously I will be replacing the valve cover gaskets so will I still have to worry about the recall problem these cars have?(I havent had the recall work done yet)Also any tips and things to look out for would be greatly appreciated!

I would think the Head Gaskets would be OK since your car has not been overheated. Just make sure when you get the UIM off that you check it for warps and replace if needed. Have you checked near the injectors for coolant seeping out the LIM gaskets?

Burning/leaking a gallon of coolant every couple weeks is too excessive. You may want to stop driving it untill you get the problem fixed in case your UIM is leaking into the combustion chambors.

Thanks! The car has not overheated and I have stopped driving it because I dont want to cause damage or risk the dreaded hydrolock condition. I am hoping to do the work over the weekend. The weather up here in Jersey is supposed to be in the 50's. I plan on keeping this car for a long time so I will just replace the upper manifold,do the lower gaskets and the valve cover gaskets.I do see what looks like oil puddled on top of the lower intake near the injectors but no signs of coolant.(I guess thats what the recall means when braking hard oil may spill causing a fire comes from these bad gaskets?)

So my questions are... should i replace the plenum or reuse the original? Should I go ahead and do the head gaskets as well while its all apart? And obviously !

And the answers are:

Replace it and you won't regret the decision not to later on. I go with the Dorman UIM Plenum kit which has all parts you need for the job. :grinyes:

On the head gaskets no unless you have the symptoms of bad head gaskets. Go for the UIM and LIM job to start.


.I do see what looks like oil puddled on top of the lower intake near the injectors but no signs of coolant.(I guess thats what the recall means when braking hard oil may spill causing a fire comes from these bad gaskets?)

No that is not what the recall implies or describes. During braking oil rushes to the front part of the cylinder heads and valve covers internally. With bad valve cover gaskets, mainly front, the oil then seeks out easier on to the hot exhaust manifolds or the area above with the plastic spark plug wire guides.

That black stuff you see on top of the LIM port runners is probably old residual coolant. It turns black after a long period of time and being heated up on the engine.

Wow. This is a big job.Wouldnt be bad if it wasnt for all the brackets in the way! Things going well though, but I probably wont get everything back together till tomorrow. Should I put thread locker on the manifold bolts? After I complete putting everything back together should I wait any amount of time before running the engine with the new LIM gasket and UIM gasket? Is there any curing time for the sealant? I really dont want to have to do this job again. Thanks!

get the cooling system pressure tested , should find the leak,

Is there any curing time for the sealant? I really dont want to have to do this job again. Thanks!

Give it 24 hours to fully cure before starting the engine.

Well, I finished the job today.This is the 1st time doing a job like this on a newer type of car. Everything went well I think? I will start it tomorrow. I followed the torque specifications in the haynes manual and it said upper plenum to intake 132in but I think I shouldve followed the paper that came with the upper plenum it said 89in. Did I screw it up by over torquing it? Also I switched everything over from the old plenum to the new but didnt realize I was supposed to replace the egr tube in the lower intake. Will this warp the new plenum very quickly? If I didnt already screw up the new plenum by over torquing it.

Technically you should use the torque figures the plenum manufacturer recommends, however, GM as of 2002-2003 started recommending using 132 in-lb versus 89 in-lb.

Since you have a 1999 you already have the smaller EGR stovepipe for the LIM so you do not have to use the one supplied in the kit. Those are for GM cars 95-98 with Series II 3800 engine with the larger EGR stovepipe.

Thanks sooo much BNaylor! You have been a big help.

just out of curiosity, is the car running? Who ever suggested leaving the heads alone, I SALUTE YOU!! My bonnie hydrolocked, i went as far as pulling both heads, BIG BIG WASTE OF ENERGY and TIME!!! replace the plenium ($145.00, install the new egr tube and new gasket and some o rings, and SUPRISE!) let us know

Well the car started right up and is running perfect with no leaks after 2 days of driving! No oil in the coolant and no coolant in the oil! Woo Hoo! Hopefully I can get another 100,000 out of this engine. Although it was a big job it was relative easy. Even replacing the stupid plastic heater hose elbows in the alternator bracket wasn't as much trouble as I thought it would be since they deteriorated and broke upon trying to remove them,I guess due to GM using Dex-cool! Next job is replacing the air conditioner compressor(since the seals in that failed and all the freon leaked out)Thanks for the help guys!

Sweet, good job! You are right, not a hard job, just time consuming. Last time I did it, on my car, I finished in just under 6 hours. If I remember right, flat-rate time pays between 4 and 5 hours only.

Hello,

I had to do the same thing which was replace my intake manifold gasket. I did it all, put everything back together, started it up and let it run for 15 minutes. Then I shut it off and it's been 2 days since i've been able to start it again. It won't start! Any advice?

Welcome to AF.

So, to clarify the starter cranks or it doesn't crank?

David,

Since your issue is already being addressed in your own thread, and is mostly unrelated to this one (your car is a GTP, this thread is for a non supercharged car), I moved your post[s] (and subsequent answers) from here to your own thread to reduce confusion for other members reading this one. Please refer to your thread here:

http://www.automotiveforums.com/vbulletin/showthread.php?t=1014536

and post any further questions/info you have there. Thanks for your future cooperation.