Radiator Cap Pressure Test

Use an adapter to attach the cap to the tester.
Increase the pressure until the indicator of the gauge stops moving.
Main valve opening pressure :

93.2-122.6 kPa (0.95-1.25 kg/m² , 13.51-17.78 psi)

Main valve closing pressure :

83.4kPa (0.85 kg/cm² ,12.1 psi)

Fig 1: Testing Radiator Cap
Courtesy of KIA MOTORS AMERICA, INC.
Check that the pressure level is maintained at or above the limit.
Replace the radiator cap if the reading does not remain at or above the limit.
NOTE: Be sure that the cap is clean before testing, since rust or other foreign material on the cap seal will cause an improper indication.