overheating on 1999 Cadillac Catera

99 cadillac catera overheated and water that come out of resevoir left an oily residue. Blown head gasket?

Asked by for the 1999 Cadillac Catera
very likely. get it leak down test to confirm.

Is this something I can do or do I have to take it to a mechanic to get it tested.
1 more answer
Bad coolant/oil heat exchanger. Common problem.