Start car, comes up to temp, turn heater on and only cold air comes out, after about 10 minutes temp gauge goes to hot, get coolant temp alarm, stays hot for a 2-5 minutes, then the needle starts dropping and a few seconds later the air starts coming out hot. After a bit, the air will stop coming out hot, then shortly after that, the car starts to overheat again. It keeps repeating this cycle.

The dealer replaced the thermostat twice. (First time was after it overheated. This weird overheating cycle thing started after the first repair.) After the second time, I just removed it. Still having this strange problem. (They also replaced the pressure cap for the reservoir...I'm also a little bit concerned this may have some contribution/cause. Wrong rating??? Vapor lock???)

A pre-existing problem that may or may not be related. Heater/front defroster would come on periodically. Been that way for almost the life of the car. The dealer never figured it out.

I'm really frustrated. Any help would be greatly appreciated.