On a very hot summer day my car started to overheat. I check the coolant and it was extremely low. I flushed the coolant and I was fine for about two weeks. I started to notice that when my car was idling it will overheat but as soon as I started going, it would go back to normal temperature. I started to try to find out what it going on and I notice that my fan was not turning on. So far, I have replace the thermostat, I change the radiator--I found a leak, and I have flushed and bleed the coolant. I do not find any leak or lost of coolant. I have jump the the connector to the cooling fan switch and the fan turns on when I set my key to the on position. I want to know if I have to change the fan switch that is on the thermostat housing, or change the temperature sensor, or if could be the water pump. I have change the oil to see if I find coolant on it and there is no coolant on the oil.

 

Fan switch on Tstat housing... replace it. You jumping the connector that goes into that switch causing the fans to come on is a dead giveaway that the switch is bad.

 

Should I change the sensor too?

 

Not needed. That temp sensor either goes to the cluster showing you if the car is overheating, or it goes to the ECU to tell it how hot the car is. Has nothing to with the fan IMO.

 

Thank you. I will change the switch and hope that it will solve my problem-I'll come back with the outcome

 

I've replaced the switch and same thing happens the fan never goes on. I try jumping the connector again and the fan still goes on. Any other suggestions?

 

I've tested the continuity on the new switch with a tester and I get no continuity. I tested it for five minutes while the car was running and made sure that hot air was blowing out of the heater. I could assume that the new switch is broken.However, I tested the old switch by hanging it in a pot of hot and I got continuity there. Could something be causing the temperature to not rise high enough on the thermostat housing that is not allowing the switch to turn on?

 

Does the engine not overheat if you jumper the switch and drive with the fan on all the time?

Lack of coolant flow (not full, clogged radiator, stuck thermostat) will not get the thermostat housing hot enough to close the switch. The engine would also overheat even with the fan running in those cases.

 

Even when the fan is not blowing my car overheats only after I drive it for a few hours and idling. So,I have not had the need to run the car with a jumped connector-I'll try next time it overheats to see if it keeps on overheating. Although, when it overheats, it goes back to normal temperature when I go from idle to moving. The radiator is new, the thermostat is new (I tested it before installation on a pot of boiling water and it opened)

 

Air in the system? How did you bleed the car previously?