Hello,

I have a '95 Lumina 3.1L w/ ~145Kmi.

I noticed a black film on the inside of the coolant reservoir, and there also seems to be a light film floating on the coolant...so I am guessing most likely that it is motor oil, since this car had the tranny rebuilt and now has an external transmission oil cooler as of a year ago.

Also, the friend I got the car from said at the last coolant flush (~2yr. ago) they told him there was oil in the coolant.

There is no noticeable performance loss of the car, no coolant found in the oil, and no coolant or steam coming out of the tail pipe.

My guess is either a leaky head gasket or intake manifold gasket.

I was told the intake manifold gaskets on these cars are prone to leak.

Does anyone know if there are any coolant passages that run along the intake manifold gasket?

Are there any tests I can perform at home to determine if the problem is with the head gasket or with the intake gasket?

Any other ideas?

A shop told me they could test the coolant for exhaust gases and that would indicate a head gasket problem if they did find traces of exhaust gases.

Thanks.

What the shop told you is the first step in the diagnosis.

Thanks, but does anyone know if there any coolant passages that flow by the intake manifold gasket on a '95 3.1L?

I am trying to understand how it is even possible for oil to get into the coolant due to a leaky intake manifold gasket.

Thanks.

How about coolant in the oil? The int gasket seals coolant passages so a leak at the gasket can cause coolant into the oil. Make sure you are not seeing trans fluid in the cooling system, the light film you see can be normal seperation/contamination of the coolant, not oil.