1999 Plymouth Breeze Car building alot of pressure

Ok to begin, My car is a 99 plymouth breeze with a 2.0 in it The thermosat housing keep breaking every couple of days but only when the car sits still for a long period idiling. Like there is to much pressure. What would you check out to see if that was the cause of the problem? Oh the radator is good. It gurggles when you park it. But is not over heating just gurggling water out of the thermostat housing that has just cracked again.