Vacuum brake boosters are used on all models except those with diesel engines.
Removal & Installation
- Remove the master cylinder.
- Disconnect the vacuum lines at the booster.
- Remove the steering column knee bolster for access to the booster mounting nuts, if necessary.
- Remove the clip securing the booster push rod to the brake pedal.
- Remove the nuts from the booster mounting studs.
- Remove the booster, spacer and gaskets from the front cowl panel.
- Reverse the removal procedure.
- Tighten the mounting nuts to 21 ft. lbs. (28 Nm).
- The remainder of the procedure is the reverse of removal.
Vacuum boosters can be checked with a vacuum gauge.
- Connect the vacuum gauge to the booster check valve with a short length of hose and a T-fitting (see illustration).
- Start the engine and allow it to idle for one minute.
- Check for vacuum at the gauge. If there is no vacuum or the reading is very low, the problem is either the booster or the check valve.
- Assuming vacuum reading is normal, clamp the hose shut between the vacuum source and the check valve.
- Stop the engine and observe the gauge. If the vacuum drops more than 1 in. (25mm) Hg within 15 seconds, the booster or check valve is at fault.
To test the check valve, proceed as follows:
- Disconnect the vacuum hose from the check valve.
- Remove the check valve and valve seal from the booster.
- With a hand-operated vacuum pump, apply 15-20 in. (381-508mm) Hg at the large end of the check valve.
- Vacuum should hold steady. If the gauge indicates vacuum loss, the check valve is faulty and should be replaced.
- With the engine OFF , pump the brake pedal until the supply vacuum is entirely gone.
- Put light, steady pressure on the brake pedal.
- Start the engine and let it idle. If the system is operating correctly, the brake pedal should fall toward the floor if the constant pressure is maintained.
Power brake systems may be tested for hydraulic leaks just as ordinary systems are tested.
- Operate the engine at idle without touching the brake pedal for at least one minute.
- Turn off the engine and wait one minute.
- Test for the presence of assist vacuum by depressing the brake pedal and releasing it several times. If vacuum is present in the system, light application will produce less and less pedal travel. If there is no vacuum, air is leaking into the system.