Plastic Parts in GM Engines

How many cars or trucks have you seen now that have these recycled plastic intake manifolds? Quite a few on the road now, right? I used to joke about 3rd party warranty insurance companies offering to cover an intake manifold because it was something that never, ever went bad. It was like a waterpump pulley or hood hinges.

Well I have a heart wrenching tale that is not finished yet (waiting for final warranty decision from GM) but it goes something like this. (By the way, General Motors knows all about this because they sell a ton of these replacement manifolds like hotcakes).

Case: 1998 Pontiac Bonneville. 65,000 miles. Clean car. 3.8 liter engine.

Problem
Plastic manifold cracks around (very poorly designed placement) EGR return tube that is cooled in water jacket as it passes thru intake housing. Over time hot exhaust gases passing thru metal pipe cause pipe to get hot and coolant enters inside of engine when plastic intake housing finally cracks due to the heat.

Engine swallows enough coolant after a hot run, owner comes come out the next morning to an engine that will not crank. Customer is handy, put a new battery and new starter motor in to no avail. Traditional diagnosis AT ANOTHER SHOP, pulled spark plugs and decided it was a head gasket after performing a pressure test (this would be a correct diagnosis in my view but I was suspicious).

Customer was adamant about not overheating this engine ever! He calls me up since now he has no car since October but has been making the payments on it anyway. I try to confirm diagnosis and my pressure test has a lot of air hissing from throttle body which prompts me to remove the throttle body and discover this engineering nightmare. This is like a $600 job if you catch it in time but since the car sat, the engine is now rusted and frozen solid.

To make matters worse owner has died of a massive heart attack and wife is picking up the pieces. Her other car is a 1996 Pontiac Grand Am which she then had to bring in a week after I diagnosed the Bonneville. The Grand Am has that quad 4 engine and it took me over 6 hours to change the lousy thermostat! Can you imagine all day for a thermostat?

I am waiting for warranty consideration after personally talking for the customer with GMAC. Of course they are giving me a bunch of bologna about this whole manifold thing but she will need a new engine if the car is to ever run again.

Everyone of these engines should be recalled and the manifold should be replaced because there is no reason on a 3-year-old car that customers should be having a blow up like this. I frowned when I first saw these plastic silly putty parts and now I know my instinct was right.

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