Radiator Cap Testing

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

Fig 1: Testing Radiator Cap On Pressure Tester
Courtesy of KIA MOTORS AMERICA, INC.
Apply a pressure of 93 ~ 123 kPa (0.95 ~ 1.25 kgf/cm² , 14 ~ 19 psi).
Check for a drop in pressure.
If the pressure drops, replace the cap.