I have the 3.9L V8 and when I first drive the car, as the engine warms up it goes to hot and reduces the engine power. But if I turn the cabin heat on hot and turn cabin fan on high the temp will stay normal, and after a few minutes I can turn it back down and everything is fine. Then if I drive the car within a few hours it doesnt do that.I also just had thermostat replaced, what could it be?
That's a real good way to ruin a motor. You can't trust that temp gauge once it gets hot because when it runs out of coolant, the temp will read lower because it can't read air. You need to have the system pressure tested to locate any coolant leaks.