Radiator Fan


Hello, everyone.

Well, my 91 corolla had a overheating problem, and mechanic did chemical radiator flushing, and he checked that pressure fine, and looks like thermostat and waterpump working fine, and there is no symptom for gasket leaking. However, overheating continues.

Today I found out that even though temperature guage is very hot, cooling fan did not kick in. I guess that cooling fan should be on high when overheating occurs. When I turn on the AC cooling fan turned on a few seconds later, however it is not in full power.

Somtimes cooling fan comes in however, it does not keep turning on enough to cool down, it just stays on about 1 min.

Anyway, is there anyway, I can make the fan on high setting always after I start the car? I’d like to see if it can prevent from the overheating. My overheating problem is so erratic. sometimes it happens when I run fast, sometimes it happens when I run stop and go. But, usually it happens when I drive long enough like 20 min.

Please anybody help me!! Thank you.


Replace the coolant temperature sender that activates the electric fan. Then the fan will come on when it should. If the fan motor is worn it won’t deliver sufficient air. You may need a new fan motor.

The fan should come on BEFORE the engine overheats.


Your Corolla is old enough to need a new radiator. Check it front and back for missing cross-fins (between the tubes). You may have to tip the shroud back after removing enough fasteners. The engineers may have designed the fan to turn off after a short time. Sounds goofy, but they’re engineers. If you have even three percent missing due to corroding away, you could have problems. Ten percent and it’s a guarantee. Pickup radiators are bigger and have more airflow, so they can have more missing fins; unless they are carrying a load.


I would like to look at something a little different. What leads you to believe it is really over heating other than the gauge? Could not the sensor be out. I don’t know about your car, but some have separate sensors for the fan and the gauge and the thermostat has it’s own.


Since I can see the boiling water in the reservoir.
Thank you.