I have a 2005 Mustang V6 with automatic trans, 93K miles on it that overheats occasionally. Mostly when stopped at idle. Car runs great otherwise.
When at the car hits operating temp and the thermostat opens, the upper and lower radiator hoses are both hot. Water pump works, with no noise or leaks. No leaks in the system. Heater blows hot, AC works and blows cold, cooling fan cycles with AC on but NOT when off.
We've flushed and burped the cooling system, replaced the Radiator cap, Temperature sensor, serpentine belt, idler pulley and belt tensioner.
After all this, the car will overheat, particularly when idling after driving around. One thing we notice is that the although the fan works with the AC on, it does not otherwise. Even when running hot and eventually overheats.
Turning the car off causes the reservoir tank to overflow and even at times thru the cap, not much but enough to need refilling twice a week.
I'm thinking now it might now be electrical. A fuse, relay, or connector or maybe Low speed thermal resistor. Any other suggestions?
The temperature sensor that turns your cooling fan on, or its associated circuitry, is probably bad.
Turning the car off causes the reservoir tank to overflow
Do not shut it off. Keep it running.
Turn the heat on full blast. Hose down the radiator with cold water. Wait until the engine drops to a more normal temperature before shutting it off.
