Cusco radiator caps

Radiator caps

The radiator caps purpose is to maintain a certain pressure in the coolant system. When the cap pressure is exceeded, the cap releases the pressure into the expansion tank. When the coolant cools down forming a negative pressure, the cap allows the flow back into the system.

High pressure caps

The original caps are usually rated to 0.7 - 0.9 bar. Cusco caps are rated at 1.3 bar.

The boiling point of water raises by pressure:
0.0 bar: 100,0 C (atmospheric pressure)
0,7 bar: 115,4 C
1.0 bar: 120,4 C
1.3 bar: 124,9 C

A higher pressure prevents local boiling of coolant in tuned engines.

There are two types of caps, so called small and big. Small caps are common on Toyota and Subaru, and big on Nissan for example. If you're not sure which one to pick, please contact our sales.