Radiator Cap Testing

Remove the radiator cap, wet its seal with engine coolant, and then install it on a pressure tester.

Fig 1: Testing Radiator Cap
Courtesy of KIA MOTORS AMERICA, INC.
Apply a pressure of 79.43-122.58 kpa (0.81-1.25 kg/cm² , 11.52-17.78 psi).
Check for a drop in pressure.
If the pressure drops, replace the cap.