Radiator Cap - Inspection

RADIATOR PRESSURE CAP

Hold the cap at eye level, right side up. The vent valve at bottom of the cap should open. If the rubber gasket has swollen and prevents the vent valve from opening, replace the cap.

Hold the cap at eye level, upside down. If any light can be seen between the vent valve and the rubber gasket, replace cap. Do not use a replacement cap that has a spring to hold the vent shut. A replacement cap must be the type designed for a coolant reserve/overflow system with a completely sealed diaphragm spring and a rubber gasket. This gasket is used to seal to the radiator filler neck top surface. Use of a proper cap will allow coolant return to radiator.