Thermal Vacuum Valve: Testing and Inspection

1. Drain coolant, as needed, until coolant level is below valve.
2. Note inlet and outlet ports, disconnect vacuum hoses and remove valve from engine.
3. Connect suitable vacuum gauge to valve outlet and vacuum source to valve inlet.
4. Cool valve to a temperature at least 10°F. below calibration value stamped on valve and apply at least 12 inches Hg vacuum to valve inlet.
5. Valve should be closed and vacuum gauge on outlet should read zero. Leakage of up to 2 inches Hg vacuum in 2 minutes is allowable and does not mean valve is defective.
6. Leave vacuum applied to valve and slowly warm valve in a pan of water while observing water temperature and vacuum gauges.
7. When valve reaches calibration temperature (stamped on valve), vacuum passage should open and gauge on outlet should indicate vacuum equal to applied vacuum at inlet.
8. If TVV or TVS fails to perform as outlined it should be replaced.