the pt cruiser keeps over heating the collent comes from under the radiator cap. i have replaced the cap 4 times, the thermostat 3 times (even tried leaving it out), the thermostat housing was replaced as well as the uper and lower radiator hose. i have just replaced the radiator as it blew out at the bottom. seems like there is alot of preasure building up. i have also flushed the system twice, the heater was bypassed as the mechanic said it was a posible cause for a leak. i don't know what else to change other than the water pump. i cant even drive 10 miles without it getting stuck. please help