can anyone tell me possible fault's that would pressurize the coolant system to the extent of it blowin it out of the header tank! after five minute's previous owner had a new rad fitted and thermostat the prob started after the rad was fitted i think it's head gasket's but any suggestion's before i start ripping the engine to pieces would be greatfull. Ta (p.s it's a wrx sti jap import estate on an auto tranny )