What to know about the radiator cap pressure test:
In a pressurized cooling system like those found on all cars, your car’s radiator cap is calibrated to seal in coolant to a particular pressure point, and thenlet some vapor to escape once that threshold has been reached. The expelled fluid is piped into the overflow bottle you might have seen in the engine bay. Then, as the engine cools, the coolant level may drop inside radiator. When that happens, a reverse-flow valve in the radiator cap opens to permit fluid from the bottle to return to the radiator. A radiator cap that isn’t working appropriately may cause too much fluid to escape the system.
Facts to Note:
A radiator cap pressure test is quick and simple, and replacement radiator caps are cheap.
Leaving a faulty radiator cap in place can cause damage to the engine.
How to Fix:
The vehicle engine is cooled before the radiator cap can be detached
The radiator pressure is relieved and the cap is detached
The radiator cap is pressure tested to specifications
The radiator cap is changed and/or reinstalled to the radiator
The vehicle is proved to confirm problem is fixed
If your car’s engine overheats, or the overflow bottle seems overly full, have the radiator (and radiator cap) pressure tested.
Common symptoms indicating you may need to pressure test the radiator cap:
Car’s overflow bottle fills up
Importance of this service:
System function correctly can over- or under-pressurize the system, leading to damage to hoses, the radiator, and even the car’s cylinder head.