Servo & Vacuum Check

To determine condition of diaphragm, remove hose from servo unit and apply 15" of vacuum to tube opening and hold in for 1 minute. Vacuum should not leak down more than 5" in 1 minute. If leakage is excessive, replace servo. Cruise vacuum switch can be tested in a similar manner.
Cruise release brake valve, resume valve, and connecting hoses can be tested by applying 15" of vacuum to each component and then sealing them off. Vacuum leakage should not exceed 5" in a 1 minute interval.