The surge tank cap (1) is equipped with the pressure valve (3) and the vacuum valve (2). Therefore, the surge tank cap maintains proper pressure. The surge tank cap protects the system from high-pressure by opening a pressure valve, and protects the coolant hoses from collapsing because of a vacuum.

1. Wash any sludge from the surge tank cap and the valve seat of the vacuum pressure valve for the surge tank cap.
2. Inspect for any damage to the vacuum pressure valve for the surge tank cap. If any damage is found, replace the cap.
3. Install a suitable cooling system pressure tester (1) to the cap using the adapter (2).
4. Pull the vacuum pressure valve to the open position. If the surge tank cap does not seal properly, replace the surge tank cap.
5. Pressurize the cap to 90-120 kPa (13-17 psi).
6. Wait 10 seconds and check the pressure held by the tank cap tester.
7. If the pressure held by the cooling system pressure tester falls below 80 kPa (11.6 psi), replace the surge tank cap.