PerformanceX2

i have a 97 escort 2.0L of course, about 190,000 miles. it overheated on me in winter when it was about -25 degrees F outside. made it home, gauge in the red, about 20 miles. problem was thermostat, had totally broken. i put in a new thermostat, drove it once maybe 15 miles and it was fine, and the next time i drove it it went to the red again after a few miles so I turned around and went home. took out the new thermostat and put it together without, so I've eliminated that as a source of problem. ran it in the garage and it heated up on me again. so what could be wrong?
-radiator is full
-no leaks
-belt is fine on water pump
-no coolant in the oil, or oil in the coolant
-compression is between 120-128psi in each cylinder
I just did the compression test today because I was told you could tell if head gasket is blown that way. But those numbers are good, correct? I'm skeptical it is a blown head gasket prob because there's no coolant in the oil. But at the same time I think the gasket prob is most likely. What else could it be?

R.S.LOGAN

A sniff test will tell if head gasket gone . Depends where gasket blown whether it mixes with oil or not .Any sign of cooling system pressurising ? Electric fan cutting in and out ?

PerformanceX2

What do you mean a sniff test? Just see if I can smell coolant when it's running? Because that would be a yes.
I forgot to add that there's no vapor coming from the tailpipe, but that could be because of how the gasket is blown, just like the oil/coolant mixing issue?
I'm sure I have coolant pressure. I had the radiator cap off, then put it on and felt the firmness of the upper hose, then started the car and felt the hose again, which heated up and felt more firm.
Oh, and the fan seems to work correctly.

R.S.LOGAN

A "sniff test " samples air in cooling system and changes colour if any hydrocarbon / combustion gases are present .Simple test to carry out in workshop .Can buy kit if needed here Universal USA Combustion Leakage Block Tester Kit New!! on eBay (end time 25-Oct-09 13:00:08 GMT). , also explains how it works . Cooling system is pressurised under normal conditions , but over pressurises if gasket gone .Usually get other signs like coolant header tank filling / overflowing , air locks , heater blowing cold etc etc .