2007 GT overheats when A/C is on (even at freeway speed)

[darien87]

Hey Guys,

Lately it's been getting hella hot here in Cali and I noticed the other day that the temperature gauge creeped up on an especially hot day, (upper 90's). Of course I had my A/C on. Normally my car sits with the temp needle right in the middle, (let's call this 50%) at all times. If it's not super hot out I can run the A/C without any issues. But on this day the needle crept up to about 75% while driving in traffic. When I turned the A/C off the temp went back to 50% after a few minutes.

Last weekend I bought some Water Wetter and added a whole bottle to the radiator. Yesterday again it was high 90's and I noticed that even at freeway speed with the A/C on the needle went up to 75%. Again I turned the A/C off and the needle went back to 50%.

The fact that the temp will go up even at freeway speed has me concerned. I searched around and saw many recommendations for the GT500 fan. But shouldn't the air blowing over the block at speed be enough to cool the engine?

By the way I don't see any coolant leaks. Also I looked at the front of the radiator and there are some fins that have been bent but I wouldn't think enough that would hamper cooling that much.

Any suggestions?

 

[Bullitt95]

Your problem isn't the fan. Overheating even at highway speeds usually indicates that the radiator core is blocked and has lost its cooling efficiency.
It's also possible that your AC condenser fins are clogged up with bugs and not allowing air to get through to the radiator. Try cleaning the condenser with a powerful hose and see if that helps before you buy a new radiator.

 

[darien87]

I looked at the radiator through the grill and the hole in under the front bumper last night and I didn't see any debris on it.

But I did notice today that when the car was already warmed up after driving for a bit and being parked, I started it up and the fan immediately came on. I then turned on the A/C because I read that the fan is supposed to turn up to high every time the A/C is turned on and it didn't. It stayed at the same speed it was at.

Maybe this is the problem? The fan is not turning to high when the A/C is on and the extra heat from the condensor is not getting drawn away like it should?

 

[don ruggles]

Replace your thermostat, check that your coolant is at least 50/50 strength, and do the bleed procedure Ford outlines. If that doesn't do it, the water pump could be shot.

 

[darien87]

I took the car to a local shop today and they verified that the fan is not turning on to high mode. Is the controller/fuse/relay that handles this part of the fan or is it somewhere else? If I replace the fan with the GT500 fan is that controller part of the fan?

 

[Bullitt95]

I then turned on the A/C because I read that the fan is supposed to turn up to high every time the A/C is turned on and it didn't. It stayed at the same speed it was at.

Maybe this is the problem? The fan is not turning to high when the A/C is on and the extra heat from the condensor is not getting drawn away like it should?

It looks like you might have two separate problems. Fixing the fan problem will improve AC function and keep the engine cool in slow city driving, but it won't fix the overheating problem on the highway.
You could try draining the cooling system, flushing it out, and refilling with fresh coolant to see if that helps. It wouldn't hurt to replace the thermostat while the system is drained.

 

[don ruggles]

Noted for corrosion of the wiring plugs at the fan connection, BUT there is a high speed fan relay that could be bad,I believe.

 

[darien87]

I tried replacing both fan speed relays. Today I tried starting the car cold. No fan. Then turned on the A/C with fan speed on 1 and the fan came on at the low speed I guess. I turned the A/C dial all the way up to 4 and no change to the radiator fan speed. Just in case the fan was spinnin faster and I just couldn't tell I measured the airflow with an anemometer and got about 6 meters/second either way.

What else might the issue be?

 

[don ruggles]

Your heater/AC fan control in the dash has no effect on the engine fan speed. It runs off the signal from the coolant temp. When on max air, I know the engine fan should be on.