uh oh, I just bought a 99 Question about intake

[lnmrmn]

I just bought a 1999 silhouette and noticed there are a lot of people talking of a water leak into the piston area due to an intake problem. Is this standard on the 3.4 v6? Also, if there are any other bugs anybody would like to share about this motor or van, please let me know.

Thanks

[cmilanese]

i have a 99 chevy venture (both are gm's) and looking at pontiac transports and montana's i am noticing a lot of intake manifold problems and that there is a belief the dex cool that GM recommends may be what is causing this problem. don't know if this will help or not.
chris

[donatelo22]

this was a common problem for the ancestors to the 3.4 liter engine.Everyone has heard of a 2.8 or 3.1 liter engine blowing an intake gasket,I've even seen rotted intakes leaking iinto the oilpan.

[sdanville]

I have a 2000, the head gasket leaked at 30,000 miles in 2002. It was replaced under warrenty. the dealer said the anti freeze should be switched to the green stuff. the orange eats the gaskets.
another mechanic said in order to pass the emission tests, GM could not use a good old breathable cork gasket..now owners are paying for it. I did not switch to green anti freeze yet. GM said the fix was a life time warrenty fix. That is because they fixed it and if it goes bad again they fix it for me in my case.

[HotDog88GT]

1998 Silhouette....poor heat caused by plugged heater core. Intake gasket replaced, two months later head gasket goes. Heat is poor again. All these problems caused by defective gasket and DexCool gumming up inside the engine. Gasket was on backorder for over a year nationwide at one point. If you haven't had that gasket replaced and you see coolant level dropping for no apparent reason, check the oil filler cap for waxy, yellowish stuff. If you have that then sell your van....

[Slammerz]

I have a 96 3.4L 85,000mi the Intake Manifold gasket failed causing coolant to leak into the oil gallery area.
Your 99 will have the same potential problem soon.
Check the inside of the oil cap for the yellow slime/foam, if it's there it's too late. If not have the cooling system professionally flushed ASAP and replace the Dexcool with regular old antifreeze, add a cooling system stabilizer like Prestone Cooling System Treatment, might not hurt to add some sealer (stop leak) too. Finally get the Intake manifold bolts torqued, some reports of them coming loose or the original specs being inadequate. Flush the system again in a year or so and replace the antifreeze more often than you normally would.

[Dan_in_WA]

Originally Posted by Slammerz

Finally get the Intake manifold bolts torqued, some reports of them coming loose or the original specs being inadequate.

I replaced my intake gaskets this weekend; with the GM gasket set came this piece of paper saying to replace the 8 lower intake bolts.

The new bolts have a different locking compound on them, which should keep them from coming loose. Torque inner bolts to 115 in./lbs. and the outer bolts to 25 N/M or 18 ft./lbs., according to same paper.

The four corner bolts on my manifold had worked loose. I think this is the root cause of my leak.