I’d been having a few nagging issues with my car lately (a ’98 Pontiac Bonneville), including a slow-ish coolant leak, misfiring on at least 2 cylinders and a subtle whining noise coming from the engine. I went up to TC last Friday and took it to the usual oil change place for.. what else, an oil change. The guys there found the coolant very low, and told me it had some discoloration to it. They also told me the whining was the tensioner pulley, and that if it wasn’t replaced soon it could seize up and break the serpentine belt. Bart had previously replaced one of the ignition coils in an attempt to cure the misfiring problem, but it seemed the wires &/or plugs needed replacing too/instead. He purchased plugs & wires at an auto parts store and on Tuesday I took my car to a repair shop near where I work.

Wednesday I got a call from the mechanic telling me that yes, the tensioner pulley was bad, and the plugs/wires should be replaced. But, the worst and most expensive thing wrong with my car was a deteriorated Upper Intake Manifold Gasket. For those interested and especially owners of GM vehicles with the 3800 Series II engine, read this article.

What happens is this: since the UIM is basically a plastic composite and literally touches a hot part of the engine (the EGR stovepipe), it degrades over time and eventually fails causing coolant to be sucked into the engine, which contaminates the oil and causes the engine to seize if not caught in time. The gist of the article is that this is not just a common issue with this engine,  it happens to every single one due to the way this part is designed. That’s fine and dandy if you drive your car a lot and it happens while still under warranty/extended warranty. In the seven years I’ve had my car I’ve only driven it around 55,000 miles total (it just rolled 80,003 when I took it to the repair shop). Not bad, but I wish I had known about this before, I might have done something about it or at least had it checked 3-4 years ago. Its going to cost around $900 to fix (including the pulley and plugs/wires).