98 cavalier overheating. please help

[mustangmike_1981]

My cavalier is running very very warm. i flushed the radiator and put in new antifreeze. at idle it does not overheat, but runs near the Hot line. once i start driving, around town it stays about the same, when i get on the highway after about a mile it starts to rise to hot. after i stop the car to check the coolant again, i can hear a popping in the overflow tank. i figured there was just air in the system, so i ran it and kept putting more coolant in. is it possible that their is a blown head gasket and air is getting in the system?? any help would be great.

thanks
mike

[mustangmike_1981]

. oh i forgot to mention, i also removed the thermostat and placed in a pan of hot water to make sure it was opening and it did. so i reinstalled that. thanks

[Mangoamerican]

try flushing your heater core

[inafogg]

with engine warmed up radiator cap off check for curculation.you should be able to tell by reving the throttle.if not possible water pump.also make sure nothing is blocking radiator(paper/plastic bag)if it only overheats at highway speeds it sounds like improper coolant/air flow.check to make sure you dont have callapsed hose some where.

[jakegday]

Originally Posted by mustangmike_1981

. oh i forgot to mention, i also removed the thermostat and placed in a pan of hot water to make sure it was opening and it did. so i reinstalled that. thanks

did you make sure that "hot water" was the exact same temperature the thermostat is rated at when it opened? what i mean is if its a 180 degree thermostat, do you KNOW it opened right at 180 degrees? or could it have opened at 200, far after it was supposed to.....?