I have a 2000 Chevy Malibu 3.1L engine, automatic. Every couple of months, my coolant level light goes off and I have to add about 16oz. of coolant mix. I have replaced the radiator cap, do not have any signs of leakage inside or out of the vehicle. Could it be that the leak is so small it is undetectable by the naked eye? If it were a head gasket leak, wouldn’t it have gotten worse at this point? It has been going on for about a year. Any suggestions?
I had similar symptoms when the intake manifold gasket on my 2000 Blazer started leaking after a coolant change. My mechanic noticed a small amount of coolant in the oil after an oil change. The dealer confirmed the intake gasket leak. The coolant displaces the oil on the crankshaft bearings leading to premature engine failure, so it should be checked ASAP.
There was a Class Action suit settlement for GM Dexcool problems. An intake gasket repair may be covered for the Malibu in Group A.
Good luck,
Ed B.