Upper plenum cracked and leaked coolant into engine

Has anybody else had V6 3.8 engine problems resulting in a cracked upper plenum resulting in coolant leaking into engine? The replacement kit was $300 and now I have a bent piston. I heard this can be a common problem for models '96-'00 because the plenum is plastic and the coolent corrodes the plastic. Pontiac says they have never heard of this problem, of course. Who knows what other damage the coolant leak into the engine might cause?

Might want to try www.clubgp.com

I thought i remember a few threads about this subject Try running a search over there and see what you get.

Wow! I guess that is just what happened to mine...Coolant got into all 6 cylinders. This is what we thought it or a gasket but after searching the web found this to be a common thing. Wish I found this out before the failure. How did you fix yours just vac and replace cover or rebuilt the engine?
I found this as a replacement seems pretty cool any knowlege on it...

http://www.1aauto.com/1A/Drivetrain/-/-/PLP1380000&specials_id=12

You can run a search here as well. A lot of people in the past few days have reported the same problems.

Wow! I guess that is just what happened to mine...Coolant got into all 6 cylinders. This is what we thought it or a gasket but after searching the web found this to be a common thing. Wish I found this out before the failure. How did you fix yours just vac and replace cover or rebuilt the engine?
I found this as a replacement seems pretty cool any knowlege on it...

http://www.1aauto.com/1A/Drivetrain/-/-/PLP1380000&specials_id=12

I am in the process of deciding what to do. Hopefully replacing a bent piston rod is all I have to do. I am now skeptical about the engine, but hope this is the last of my troubles.

I just had this happen to my '97 GP GT. I also had to replace the lower intake gasket. From the sounds of it, I can assume this is a pretty common problem with a '97 GP? The Pontiac dealer told me they have a new designed part for this. What are the old of this happening again? One of the reasons I bought this car was for the V6 3800 engine. I read it was suppose to be one of the best made engines......NOT!! My car is not even 8 years old....Why to go GM!!!

i work at CarQuest and we sell these replacement manifold ALL the time.
Dorman makes an improved version that is reinforced in the typical problem area.
I have never had defective return on these parts.
Retail is $193. but you could probably find it for less if you shopped around.
Part # is 615-180 comes with all gaskets needed to change it.
It fits all series II 3800 motors.
Hope this helps...

Should this be replaced before such a problem occurs, i have a 97 GP GT, what are the odds of this happening to my engine? Should i replace such a part since the odds are so great?

Should this be replaced before such a problem occurs, i have a 97 GP GT, what are the odds of this happening to my engine? Should i replace such a part since the odds are so great?

If it were mine id do it.Wouldnt want to take a chance on any internal engine problem's,unless you want to build a new motor :wink:


~Larry~

Wow these cars have alot of problems...

Is the replacement of this part a very serious task or could I do it myself?

Is there any way i can easily check to see if my car has this problem without completely dismantling something?

The easiest way to determine if you have a cracked intake is to take the throttle body loose from the intake and inspect the two coolant passages between the intake plenum and throttle body. IF the passages have a rough surface, they are starting to erode, and you should change it before it does major harm This is the problem area and will occur on 75-80% of these engines. Just another example of GM trying to cut corners and screwing the pooch.

Holy %^&* its that frequent? and my car is 8yrs old? So its a guarantee that it will eventually happen?

The reason why you had coolant leak into your engine is this :

1) New formulated coolant is Dex 3 and it is a plasticizer. This means that it alters the molocules of the plenum; softens them up and then they leak.

Don't check at 60k 80k 120k for simple things like this will always lead to cataclysm...

Every dealer is paid to tell you they don't know this:

Check the disclaimer recall on any plenum since and 90% have a recall because in fine print they admit, it is a plasticizer.

if you look back at the recall list for grand prix's mine was a 97 grand prix gt 4dr. got mine replaced a few months after the recall for free. the put a new upper plenum in which has an aluminum inside coating instead of the plastic.

along with recalls the did things for power steering and a spark plug wire which if engine oil leaked could start a fire.

don't know for sure if they will still do recalls on those cars due to the time length but just some info out there for those if you want to try.

http://www.motortrend.com/cars/1997/pontiac/grand_prix/recalls/index.html