A quality radiator, like Northern Radiators' will do it's job best when part of a quality system. An over pressurized radiator is usually the first sign to a larger mechanical issue. Most often it is the first sign to a blown head gasket. More rarely it is the result of a worn radiator cap. It is essential that a new cap always accompany a new radiator. For more information please see How to select a radiator cap.
Properly pressurized radiator Notice the clip tightly against the tank wall
Over pressurized radiator Notice the ballooning of the header between tubes