i actually had the same question, i read the thread i actually have this problem with my car, its a 1996 mits eclipse, just got a brand new radiator, water pump, but it tends to build up pressure in my overfill and then dumps it out, then i get less coolant in my radiator causing my car to overheat, it is an electric fan and i was thinking that it might not be kicking in as often so that may be the problem, could it be just a new radiator cap? if you guys can help me out that'd be terrific. i'll try the heater core flush. that may be the prollem!??
it could be the radiator cap, or the thermostat, or a bad radiator, or a bad fan, or ...........
