So as the title states, I have yet to hear my electric radiator fan turn on. Driving at high speeds my temp stays around normal, but as soon as I get off the highway and start driving slower the temp creeps up to overheating levels.

I have already replaced the fan itself, fan fuse, water pump/engine fan/fan clutch, coolant temp sensor, PCM/ECU, AND flushed the coolant system completely.

After replacing the water pump and flushing the system the problem seemed to disappear for 3-4 days but now it's back.

Any ideas on what could cause the electric fan to not work? Or how I can solve this issue another way?

 

What engine?

Does the fan motor run if you jump it?

How about the fan relay?

 

It's got the 4.7L v8 engine. What do you mean by jumping it? Hooking power directly to the fan? How would I do that to test it? Not sure about the relay either.

 

Grab some wire and hot wire the fan to the battery. See if it actually works. New or not the motor might be bad.

Then check the relay located under the hood in the PDC. The contacts can fail.

Do you have a meter?

 

I do have a meter. But I am starting to come under the impression that the radiator fan is not the issue. I've noticed that after running fine for a few days, once it starts to overheat I always check the coolant and it's about 1/4 - 1/2 gallon low. I top it off, and runs fine for a few days again. The CONFUSING part is, I have never seen a leak. What happens is, the coolant gets pushed out of the system through the radiator cap and back into the reservoir, which starts to overflow. Do you think the radiator cap could be faulty?

 

The coolant is supposed to be drawn back in as the engine cools. Yes, it could be a bad cap. Get a name brand, OEM if possible.

You might also want to pressure test the system, just to be sure there are no leaks.