[pnoye2]

The raditor cap is brand new,although I think autozone gave me the wrong one. It does not seem to hold on a snug as the old one did.

Yes, I did replace the thermostat (about 5 months ago).

I got the stop leak for one reason:

The radiator was spraying coolant out if the top as soon as the engine was warm. I can't afford to buy antifreeze everyday, and I can't just put water in it because it would freeze.

I am about ready to buy a new thermostat. I'm starting think the one I got was a dud.

I'm with arcinguy, blown head gasket...