Radiator Pressure Cap Testing

Radiator Pressure Cap Testing

Special tools, testers and auxiliary items required

• Cooling System Tester (VAG 1274A)

• Cooling System Adapter (J-48840)









The cooling system tester (VAG 1274A) is very sensitive to small air leaks that will not cause cooling system problems. A pressure cap that does not have a history of coolant loss should not be replaced just because it leaks slowly when tested with this tool. Add water to the tool. Turn tool upside down and recheck pressure cap to confirm that cap is bad.

Assemble the cooling system adapter (J-48840) to the cooling system tester (VAG 1274A).

Dip the pressure cap in water. Clean any deposits off the vent valve or its seat and install the cap to the cooling system adapter (J-48840). Working the plunger, bring the pressure to 104 kPa (15 psi) on the gauge. If the pressure cap fails to hold pressure of at least 97 kPa (14 psi), replace the pressure cap.

If the pressure cap tests good while positioned on the cooling system adapter (J-48840), but will not hold pressure or vacuum when positioned on the filler neck. Inspect the filler neck and cap top gasket for irregularities that may prevent the cap from sealing properly.