Radiator caps

All radiator caps are vented but the some caps have a gasket that seals to the outer ring of the radiator neck so the cap is sealed to the vent hose and catch tank. When the water gets hot it expanse so it goes into the catch tank, when the water cools it retracts so because of the gasket on the outer ring it can draw the water from the catch tank so the radiator always stays full. The chrome cap you have must not have he outer gasket so it leaks around the edge.

Chuck