Thread: LIM Gasket Causing Coolant in Cylinder?

I just acquired a 1999 Grand Prix. Engine Hydro Locked. My immediate thought was Head gasket. I pulled the Intake and rear Head off and couldn't find a distinctive crack. When I removed the upper plenum i found the lower manifold filled with coolant. I inspected the head and cylinder and found no distinctive cracks. The car has been well maintained. I am puzzled. I dont want to waste the cask on a gasket set to find out it is something else.

Any Ideas.

If the LIM has water in it then you have a bad LIM gasket. It's a common problem with These cars.

What type of motor fo you have? 3800 lower intake are suppose keep coolant on the inside. If you have coolant in your cylinder and there are no apparent cranks along the wall. You wll have to replace your lower intake gasket. I recently did the job on my ponitac. But I also changed the head gasket seal aswell as my lifters and push rod. If you do the job yourself make sre you torque to spec or you will ahve to tear it all down again.

I do have the 3.8L. I am going to pick up a manual to make sure I do the Torque Specs correctly. I probably wont tear down the front bank since apparently I didnt need to tear the rear head off. I will check compression though. Hopefully it is the LIM Gasket. Hate to waste all this time for a bad engine.

It could be the lower intake manifold (LIM) gaskets. As has been said, factory LIM gaskets were a nylon material. That nylon will fail in 100% of cases, it's just a matter of time. Replace those with the newer aluminum type, which can be gotten at a dealer or through online sources like ZZPerformance.com or intense-racing.com.

(Don't get FELPRO "updated" style LIM gaskets; they're still nylon)

It could also be the plastic upper intake manifold (UIM) itself (or the UIM gasket) . Over by the throttle body (TB) end, coolant flows up from the LIM, through the UIM gasket, into the UIM, through the TB, back through the UIM and UIM gasket, back into the LIM. All the while it flows around the EGR stovepipe coming into the UIM from the LIM. The UIM plastic in that area (and sometimes the UIM gasket also) melts/warps/cracks, allowing coolant ingestion. The plastic face where the TB attaches also can warp from heat, allowing coolant ingestion at the TB gasket.

Best easy/cheap fix for that is the Auto Parts Now (APN) replacement UIM kit, which comes with new UIM gasket, TB gasket, and a steel-sleeved EGR passage in the UIM and a special reduced-diameter EGR stovepipe for the LIM (these last items reduce the long-term tendency toward plastic meltage in that area).

I got no link, but there's a video of a guy doing a LIM on a SC 3800. I think it's on here. Anyone got the link?

Well I have it just about together again. Unfortunatly I did use Fel-Pro. Hopefully it lasts a while. I hope it runs after this it has been awhile sine doing head job. And hopefully my wife lets me keep the car. It was originally an investment project since I was given the car and could probably sell it for $3000.

After ripping the engine apart and putting it together it turns out I need a new plenum. It has a nice hole

Do you guys think I can JB weld the hole? Do you think it will hold?

That was a good video. Thats one hell of a job. I think I read several articles about Law Suits pertaining to DEX-COOL becomming corrosive and damaging Intake Manifold gaskets. It seems that its not so much DEX-COOL but the material the gaskets are made of. I had an 03, 3.1 base model Grand Prix I sold it at 73000 mi. I never noticed any cooland mixing with oil. I did maintain that car pretty well. I now have an 07, Grand Prix GT I've heard the Manifold gaskets on the series III vehicles is a better material. So what do ya all think, was it DEX-COOL or the gaskets? I have about 32000 mi on my GT should I just stick with DEX-COOL or go with the conventional Green Coolant.

Dex-Cool began in 1996. Series 2 3800 was put into H-bodies starting in 1995. Yet I've seen a few 1995 H-Bodies--which never touched Dex-Cool--whose LIM gaskets and UIM's are as bad as any from 1996+ Dex-Cool-ed 3800's.

My conclucsion is that it's the nylon the gaskets and UIM were made of breaking down from heat, not so much the DEX-COOL.

Many say that Dex-Cool causes sludge and build-up. I don't believe that either; I believe that "crud" is from the sealant pellets dealers threw into the coolant system to try to mask leaky gasket symptoms and outlast the warranty.

I've seen a fair share of cars with "dexmud" in them, but a good chunk of them were still running the same coolant over the entire time of ownership

On a car that's been maintained well, I have yet to see it