Remove the radiator cap, wet its seal with engine coolant, then install it on a pressure tester.
Apply a pressure of 93.16 ~ 122.58 kPa (0.95 ~ 1.25 kg/cm², 13.51 ~ 17.78 psi).
Check for a drop in pressure.
If the pressure drops, replace the cap.
Wait until engine is cool, then carefully remove the radiator cap.
Fill the radiator with engine coolant, then install the pressure tester on the filler neck.
Apply a pressure of 93.16 ~ 122.58 kPa (0.95 ~ 1.25 kg/cm², 13.51 ~ 17.78 psi) to the pressure tester.
Inspect for engine coolant leaks and a drop in pressure.
If coolant leak or pressure drop is occur, replace the part.
Check for engine oil in the coolant and/or coolant in the engine oil.