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Recently my car started chugging and "vibrating" at low speeds, and the check engine light is flashing on and off. On inspection, I found oil in the coolant. I don't know a lot about cars, but a somewhat knowledgeable person I know, and this question indicate that it's a sign of the head gasket starting to go. I'd like to be sure, though.

My question is, is the problem almost certainly the head gasket, or could something else be wrong?

EDIT: The engine is a V6.

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oil IN THE coolant? or coolant IN THE oil? This is a very important detail. – cinelli Jun 23 '13 at 23:09
It was definitely oil IN THE coolant. – Meta Jun 23 '13 at 23:42
up vote 3 down vote accepted

Oil found inside the Cooling System is typically caused by leaking Intake Manifold Gaskets and sometimes the Intake Manifold itself is cracked/damaged. It is a very common issue with these vehicles. It's not a job I would recommend someone do at home unless you have the tools and experience to confidently perform the repair.

Here is an example of what the intake gasket set looks like. You didn't list engine size in your original post.

enter image description here

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It is a V6 engine. – Meta Jun 24 '13 at 1:30
Common issue as @cinelli says with the 3.8-liter V6 in GM cars from that period (1995-2002 or so), less common but still not unheard of with the 3.1-liter V6. The good thing is that since it happens so frequently, you should have no problem finding a mechanic who has done the job before and can do it for minimum cost. If the car is otherwise in good condition, it's worth replacing the intake manifold—the GM V-6, apart from this particular problem, is a good reliable engine that will last a long time. – dodgethesteamroller Jun 24 '13 at 18:48

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