Thermal Vacuum Valve: Testing and Inspection

1. Disconnect and plug hose No. 31 from vacuum control valve.
2. Disconnect vacuum hose routed to air control valve B from the vacuum control valve, then install vacuum gauge to vacuum control valve.
3. Start engine and allow to reach normal operating temperature, then check for vacuum at idle. Vacuum should not be present.
4. If vacuum is not present, proceed to step 5. If vacuum is present, check hose No. 15 for blockage, leaks or improper connection. If hose is satisfactory, replace vacuum control valve and repeat test.
5. Raise engine speed to approximately 3,500 RPM and close throttle suddenly while observing vacuum gauge. Vacuum should appear momentarily.
6. If vacuum appears, control valve is satisfactory. If vacuum does not appear, check vacuum lines No. 15 and 19 to intake manifold for blockage, leaks or improper connection. If hoses are satisfactory, replace vacuum control valve and repeat test.