Hey everyone. I have a little problem and wondering if someone can help me. I have a 93 Integra and here is the weird problem:
1) the radiator fan does not turn on when the engine is on even if on for an hour
2) the radiator fan turns on ONLY when the engine is off =P
3) the coolant reservoir bubbles like boiling water
4) the temp gauge inside does never goes above half
5) and i just changed the thermostat
Me and my friend spent many hours trying to figure out why this happens. can someone be kind enough to show me the way because im stuck... i appreciate the help

 

OK, some comments:

1. The radiator fan is operated by a temperature switch. Its operation is independent of the engine. It doesn't care if the engine is on or off, but just the temperature of the water in the radiator.
2. It is not unusual that the radiator fan comes on when the engine turns off. Its because while the engine is running, the water pump is circulating water, the car is usually moving which passes air through the radiator, cooling the water. When you stop and turn the engine off, the water is no longer circulating and it gets heated up fast.
3. Some bubbling is normal.
4. If your cooling system is in great shape, which it sounds like it is, and your water pump is moving water nicely through the system, and your radiator is efficiently exchanging heat, your thermostat is opening to keep the temp correct to spec, then your temp gage will show normal operating temp. I had my whole fan completely out of the car for 2 months while I was replacing the motor and the gage never moved any hotter than ever. (course, that was wintertime)
5. OK. Hopefully you bought the correct operating temperature stat for your car.

Sounds to me like everything is working correctly.

 

Your fans should come on after an hour of just idling. Check your thermo switch to see if its bad. If it is then the fan won't turn on at all. Also check to make sure all the ground wires are hooked up. This can cause the same thing. Did on a friends car.

 

Sounds like your cooling system is running great, but I'm not too thrilled about that fan problem. The fans not turning on at all while at idle for an hour might suggest a problem, but if the coolant temperature is staying cool enough then, your fans will never come on. Just check out all of the obvious things, the fan and condenser relays, fuses, coolant temperature switches and wiring. Good luck.