Overheating Geo Storm

I have a 1990 Geo Storm with an attitude. It has a heating proble that nothing seemed to be working to resolve this problem.

I have replaced a radiator and cap, the thermostat, water pump and timing belt, fan relay and the temperature sensor, the head gasket, several hoses still no dice. It overheats and boils over as soon as the A/C is used. the guage goes rapidly to RED. If the A/C is not used, it remains in the middle. The engine is strong and it passes emission (Smog)test. Am I missing something here? I don’t know what else to check. E-mail your responses to me.

Thanks for your time.


The first thing to look at are the radiator cooling fans. They should operate whenver the A/C is on; if not, the engine will overheat.

If the fans are operating, then the next thing would be knowing if the car overheats only on the open road or if it overheats both on the highway and with in-town driving.

If the fans are working and the car only overheats on the highway then I would look underneath and see if the vehicle has a missing radiator air dam. Many pointy nose vehicles use them and their purpose is to force air upwards and through the radiator. Critters and curbs take care of a lot of them.
A missing dam will not cause overheating problems in town, only on the highway.

Also make sure the water pump is really working…

The car is old enough that the impeller could be rotted or broke away.


Maybe you A/C is damaged and binding in such a way that it requires major “effort” from the engine to run the compressor. If you pull the fuse on the A/C and drive it around for a week or so, with no overheating problems, your answer is that the A/C is defective. Good luck! Rocketman

Thanks to all that responded. The car finally died, after all the work-head gasket/ water pump, radiator, hoses, fan relay, thermostat, temperature switch and seven hundred in the whole. This was less than two weeks out of the shop. It was still overheating.