Ok, so I've been dealing with this issue for a couple of weeks, which is brought me here. It seems to only overheat from a standstill, though if it's hot enough out, it will do it on a long drive as well. There are no leaks, no white smoke, and no sputtering, so I've pretty much ruled out a bad head gasket. However, I have replaced the hoses, the radiator, and the thermostat and still it overheats. Coolant is topped and I've bled the system to the best of my ability (though whether running the engine on an incline with the radiator cap off is the proper way or not, I leave you to decide). I have noticed that the cooling fan does not seem to come on until the engine is almost in the red. Tonight, I swapped the cooling fan relay with the A/C fan relay and the A/C fan still comes on when it's supposed to, so I think the relay is ok.

As I said, there are no leaks and I'm not losing coolant, so I don't think the water pump is at fault. Also, the coolant coming out of the engine leaves the hose hot to the touch, while the one coming out of the radiator is pretty cool, so I'm confident there is proper flow.

The only thing I haven't checked (and I have purchased the part) is the fan temp switch in the thermostat housing. That's my next step and if that doesn't work, I'm nearly out of ideas. Could it be the coolant temp sensor, or the ECT sender? How likely is that and is there an easy way to test?

This is making me crazy, but for a first project, I'm learning a lot about our cars, so that's good.

 

ya i would bet that its the temp switch. but then again with cooling systems they are a pain. could be a million things (literally) have you checked for power and ground? could maybe be a bad wire connection somewhere. but i would almost bet that its the temp swtich.

 

I just ran the temp up to about 80% and the fan never came on. I assume that it's either the fan switch or the fan motor. I just took the radiator out to replace it. I seriously hope I don't have to do that again, lol.

 

easiest fix is to run a wire from fan to a acc. wire when you turn your key on then the fans come on. some hook up into the fuse box and others hook up into the ignition wire.

 

Thats sounds really "jerry riged" Im not sure I would do this Probably end up burning out the fan motor and ending up at square one again.

I would find the root problem, I had a similar problem where mine would redline then go back down and gauge would not register anything steadily. It turned out the the Temp sending unit (8 dollars at autozone) was bad. Is it actually overheating and shutting off? could the guage just be bad? Not sure just trying to help trust me bro I know how frustrating cooling systems are!

 

no it wont burn the fans out all its doing it when you turn the key on the fans automatically come come..

 

Car has never shut down from overheating. I just shut it off before it gets too dangerous. Anyone know what size the bolt is on the fan sensor? I tried 18mm and it was too small. Looks like 20-22mm but I can't tell for sure. I suppose I could take the thermostat housing off again to get to it....

 

Don't modify the wiring. The system works great stock as long as all the parts are OK. Find the problem and fix it right. The fan motor life will be shortened by running it all the time, and it is a rather expensive part.

Unplug the temp switch and put a jumper in the plug. The fan should now come on as soon as you turn the key on and run all the time. If the fan doesn't work, troubleshoot the circuit (fan motor, relay, and fuse)

If the fan does come on and run, test drive with the jumper in place to see if there is any overheating. If it doesn't overheat, replace the thermal switch. If it does overheat, verify that the fan did indeed stay running.

 

Ok I hope this logic works for you. I repair electronics on Army Radars to include cooling fans. Regardless a electric motor is an electric motor wether on a car or a radar. They work on the same principle. I understand that if you wire it this way it will turn on, the problem is that it stays on so long as the car is running. So when you are driving for 2 hours , your fan runs for two hours straight with out stoping significantly decreasing fan life, where as if wired correctley it would only come on a 1/4 of the time significantly increasing fan motor, bearings, etc life time.

I would not follow his advice.

 

I'm gonna try that just to see if the fan motor still works. At least that way I know that it's either the fan or the fan switch. I still think it could be the coolant temp sensor or the ECT sender. Either way, I'm sure it will be the last possible thing I can replace just to make sure I spend as much time and money on it as possible, lol.