If you had a bad head gasket it could be leaking internally and not show up on the outside of the motor. You would also be refilling the coolant resivoir and the engine would smell hot.
If the thermostat was sticking open you would not have as warm of coolant until you were running in traffic or at idle because the air was not blowing through the radiator as fast allowing the engine to heat up more. This roller coaster stop and go driving would also cause the temperature gage to rise and fall accordingly.
If the thermostat became unstuck on its own, the problem would go away.
A bad head gasket only gets worse and never ever goes away by itself.
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Monday, March 17th, 2008 AT 8:53 PM