Radiator Cap Service Video

The radiator cap is a small pressure valve that keeps the whole cooling system working as designed. By holding roughly 13 to 16 PSI, it raises the coolant's boiling point so the engine can run hot without boiling over. This video shows a worn cap next to a fresh one and the pressure test that confirms whether yours still holds.

The cap seals the radiator or pressurized expansion tank with a spring-loaded valve set to a specific release pressure. As coolant heats and expands, the cap vents the excess into the overflow reservoir. When the engine cools, a second vacuum valve opens and pulls that coolant back in.

Unexplained coolant loss with no visible leak is the most common clue, and overheating on hills or under load is another. Grant County's hot summers and cold winters put the spring and seal through wide heat cycles until the seal hardens. If overheating has already damaged other parts, radiator repair is the natural next step.

A cap that releases too early pushes coolant into the overflow tank, sometimes as vapor you never see. It also lowers the coolant's boiling point, so the system boils over at temperatures it should handle easily. With less coolant in the system, the gauge starts creeping up on long climbs.

Affordable Automotive Services pressure-tests the cap with a hand pump and the correct adapter, checking whether it holds rated pressure for 30 seconds. We then test the system itself, so we know which part is actually leaking. The cap is one piece of our cooling, AC, and heating repair services, and we check it during every coolant service.

A cap that cannot hold pressure gets replaced with one matched to the PSI rating stamped on the original. We never substitute whatever happens to fit the filler neck. A failed cap is a small repair, while a missed one can lead to a warped cylinder head.

Call Affordable Automotive Services at (509) 764-0000 to have your radiator cap pressure-tested. Drivers from Ephrata, Quincy, and Warden count on Moses Lake car care that catches cap failures before they become engine failures.