Vacuum System Testing

Fig 6 Adjust Vacuum Test Bleed Valve:

VACUUM TESTING
Use an adjustable Vacuum Test Gauge (C-3707) and a suitable vacuum pump to test heater control vacuum. With a finger placed over the end of test hose, calibrate vacuum control valve on the test gauge to obtain -27 kPa (8 in. Hg.). Release and block the end of the test hose several times to verify vacuum setting.


VACUUM TESTING THE ONE-WAY CHECK VALVE
1. In the engine compartment, disconnect the vacuum supply (black) hose.
- This hose passes through an opening in the dash panel.
2. Remove the vacuum check valve.
- This valve is located on the (black) vacuum supply hose at the right side of engine.
3. Connect test vacuum supply hose to the control module side of the valve.
- In this direction the gauge should return to calibrated setting.
- If valve leaks vacuum in this direction, valve replacement is necessary.
4. Connect test vacuum supply hose to the engine vacuum side of the valve.
- Vacuum should flow through valve.

LOCATING VACUUM LEAKS
To locate a vacuum leak, disconnect 7-way vacuum connector behind the instrument panel at the A/C Heater control. For removal and installation of A/C Heater control panel, refer to Instrument Panel. Connect the calibrated vacuum hose prod to each port in the vacuum harness connector. Some vacuum circuits have a metal fiber restrictive device located in the line. More reaction time is required for the test gauge to return to calibrated setting. After each connection is made, the test gauge should return to calibrated setting. If all circuits function properly, replace control mode vacuum switch. If not, determine the color of the vacuum circuit that is leaking. To determine vacuum line colors, refer to the A/C Heater Vacuum Circuit Control chart. Disconnect the vacuum actuator at the other end of the circuit. (Instrument panel removal may be necessary to gain access to some components). Block the end of the disconnected vacuum line. The test gauge should return to calibrated setting. If not, that circuit has a leak and must be repaired or replaced. If test gauge returns to calibrated setting, the vacuum actuator must be replaced.