this is really weird. my car is overheating but only when im idle, like sitting in traffic. but it doesnt really overheat, the temp gauge just goes into the red. i have yet to see any steam coming from the radiator. once i start going again, it drops down again. also, i just drove 2000 miles from denver to phoenix and back in like 110-120 degree heat without any problems. wtf is goin on? radiator fan works, just changed the thermostat, and a/c is not being run. any help???