Intake manifold taking on oil and water

My 1995 Bonneville (just about to turn 100,000 miles) was acting like it had a head gasket leak with white smoke and losing water, but no water in the oil. When I removed the upper part of of the intake manifold (the black plastic part) there was oil and water in the belly of the metal lower portion of the intake manifold. The bolts between the upper and lower intake manifolds were not very tight. I now beleive this is where the water and oil were entering the combustion chamber and causing white smoke exhaust and oil on the spark plugs.
1. Is this a common problem? Is tightening of the upper intake manifold a regular maintenance thing?
2. Since I have gone this far, should I go ahead and yank the heads for a valve job? The lower metal intake manifold and heads are still in place.

Yes!

Many of the Bonnevilles, Grand Prix, Olds 88, Luminas all had intake manifold gasket leaks, I found the kit cheaper from the dealer and they may also recommend changing the intake bolts also.

Depending on how many miles/kms are on the car would determine if pulling the heads is nessassary.


Good Luck

Mr.Rob

Lic Mech Auto/Truck/Trailer Ect....

Thanks Mr. Rob. I think I will foregoe the valve job since the engine has been running very well (until this) and I take pretty good care of it.
When I put this back together, should there be oil in the belly of the lower intake manifold to catch foreign matter that might make it in the intake? or should it be dry?

The chamber should be dry. Search this forum and the Buick forum for threads regarding this problem. It is very common on the 3.8

A couple of months ago I noticed a smell of coolant coming from the engine compartment of my 99 Bonny 3.8 and after looking around the radiator area, I took of the decorative engine cover and discovered a small quantity of coolant around the intake manifold.
I searched the web for the subject of coolant leaks on Bonnevilles and found this great site. Reading some of the horror stories about expensive repairs people had from coolant leaks prepared me for the worst.
I'm glad to report that simply replacing the upper manifold gasket and cleaning all contact surfaces, about a four hour job for a newby, made my Bonny is well again. My repair was relatively painless and my engine did not suffer any damage from the leak, and I am greatful to all who shared their experiences on this board.

You might want to inspect the plastic upper intake also. Last year I replaced one that had a pin hole in it allowing coolant to go into the intake. The factory one was faulty. I think there is a recall, (check with dealer). The aftermarket plenems are reinforced in that area.

You might want to inspect the plastic upper intake also. Last year I replaced one that had a pin hole in it allowing coolant to go into the intake. The factory one was faulty. I think there is a recall, (check with dealer). The aftermarket plenems are reinforced in that area.

Wilfie27, thanks for the warning, I hope I don't have to take the plenum off again. I did inspect the plastic plenum, but a pinhole could be missed. I'll keep my fingers crossed. I don't there is a recall, though there should be. Pretty low of GM for letting this go on. Anybody ever thought of a class action lawsuit?

My sister-in-law received a letter from her dealer that if you had to have that work done you can be reimbursed, just mail in a copy of the bill. Next time I talk to her I'll get more info.
You should feel lucky, I thought it was the head gasket and replaced them only to have the same problem. Then a sales rep where I work, (Jasper Engines) said that is a common problem. I wish he had told me before I replaced the head gaskets.

This problem is very common with all non supercharged 3.8's. This gasket, and the plenum itself warp, causing such problem. You have to replace the upper plenuem, gasket and possibly the lower plenum. when you get the new gasket, it has been upgraded to work better, but it also means wether the upper is warped or not, it has to be replaced, because the new design wont work with the old plenum. it is very common, even parts guys know the solution without hesitation. Not a recall item btw.

I found a repair kit from Ken-Co that will fix the coolant leak in the upper plenum and gives a new, smaller tube for the EGR exahust so that it doesn't come in contact with the plenum. They don't sell direct to the public so you have to find the distributor in your area, but I never did call and get a price. I decided to go with a new plenum.
I found a new and improved intake plenum at ebay motors which I ordered and got three days later. It was $135 (including gaskets & shipping) compared to the dealer price of $225.
I almost have everything back together, but I am changing the serpentine belt while I have the extra room to play with. So I will be searching the forum for any tips on removing the side motor mount :mad: to replace the belt.
Thanks for everyones helpful comments.

Well, the new plenum did the trick. It took a while for the water in the exhaust system to get out. I was able to replace the belt - see 1995 Bonniville serpentine problem.

I just found out my 3.8 intake manifold is also leaking. harry123-- Will the aftermarket intake fix leak again at the EGR port after many miles later, and is the aftermarket intake made better and who did you buy it from?