Thermal Vacuum Valve: Testing and Inspection

With the engine cold:
1. Connect a hand operated vacuum pump to the thermo-vacuum valve (located in the upper coolant hose outlet, near the thermo-time switch).
2. Apply 300 mm (12 in.) Hg vacuum to either side of the thermo-switch.
3. With the engine COLD, thermo-vacuum valve must hold vacuum. If the valve leaks, replace it.
4. Start the engine and let it reach normal operating temperature.
5. With the engine warm (coolant fan should cycle on and off once):
6. Both thermo-vacuum valve ports should be open, (the valve should not hold vacuum).
If the valve is blocked, replace it.