Cadillac Repair: Cadillac, coolant system, head gaskets

Question
We have a 1992 Cadillac Concours. It runs perfect but over heats as soon as the engine warms up. There is NO oil in the water, it is not even grey. We have replaced the water pump and we have put 2 thermostats in. The last one opened at the boiling point in a pot of water.We are at our wits end. This is an otherwise very good car. HELP!

Answer
What you are looking at is engine cylinder combustion chamber pressure getting into the coolant syatem via small leaks in the head gaskets. Have the coolant system tested for pressure loss using a radiator pressure gage and if you have pressure loss, You have blown head gaskets. A very common fault with Cadillac engines.