Antifreeze backs up into the reservoir tank and it overflows.......please tell me its the thermostat.

 

we can tell you its the thermostat but it may not be right.

Have you done anything to the car recently? Are there any leaks? Any idiot lights?

 

You say it's overheating.. can you see it overheat on the temp gauge?

 

Yes it was overheating on the temp gauge, but I wanted to start with the cheapest part and it wound up being the thermostat. It was sticking intermittently and not allowing the coolant to flow which caused it to backup in the reservoir tank. Thanks guys for responding.