My 2003 protege (LX I think) overheated yesterday, the lower hose was cool when the engine got past normal operating temperature so I replaced the thermostat, it still overheated. Today I actually tested the thermostats in some boiling water the old one didnt open even though it was a lower temp (180F-82C for the old; 192F-88C on the new) the car still starts to overheat. Is this a common problem with this engine?

I started the engine with a garden hose feeding water into the radiator cap and the upper radiator hose off, cranked it and it was pumping water So it is pumping water, and the thermostat is working.

Any ideas?

I had a cadillac with a northstar V8 and those had a habit of anytime something in the cooling system would malfunction they overheat and the headgasket blows.

What are the odds of the head gasket being blown?