Except Federal 4WD
- With hoses removed from both ports of VSV, blow air into each port of VSV and check that air flow is blocked in both directions. See Fig 1 .
- With engine running and coolant warmed above 147°F (64°C), reconnect hose between thermo vacuum valve and VSV. Blow air into other VSV port and check that air flows through VSV and thermo vacuum valve circuit. Replace VSV if it does not operate as outlined.