Radiator Cap Testing

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

Courtesy of KIA MOTORS AMERICA, INC.
Apply a pressure of 79.4-122.58 kPa (0.95 - 1.25 kgf/cm² , 11.5-17.78 psi).
Check for a drop in pressure.
If the pressure drops, replace the cap.