Vacuum Brake Booster: Adjustments

NOTE: Master cylinder pushrod-to-piston clearance must be checked and adjustments made, if necessary, before installing master cylinder.

PUSHROD CLEARANCE ADJUSTMENT
1. Set the special tool on the master cylinder body; push in the center shaft until the top of it contacts with the end of the secondary piston by turning the adjusting nut.





2. Without disturbing the center shaft's position, install the special tool upside down on the brake booster.
3. Install the master cylinder nuts and tighten to the specified torque.
4. Connect the brake booster in-line with a 0 - 101 kPa (30 in. Hg) vacuum gauge to the booster's engine vacuum supply, and maintain an engine speed that will deliver 66 kPa (20 in. Hg) vacuum.





5. With a feeler gauge, measure the clearance between the gauge body and the adjusting nut as shown.
Clearance: 0 - 0.4 mm (0 - 0.02 inch)

NOTE: If the clearance between the gauge body and adjusting nut is 0.4 mm (0.02 inch), the pushrod-to-piston clearance is 0 mm. However, if the clearance between the gauge body and adjusting nut is 0 mm, the pushrod-to-piston clearance is 0.4 mm (0.02 inch) or more. Therefore, it must be adjusted and rechecked.

6. If clearance is incorrect, loosen the star locknut and turn the adjuster in or out to adjust.

NOTE:
- Adjust the clearance while the specified vacuum is applied to the brake booster.
- Hold the clevis while adjusting.

7. Tighten the star locknut securely.





8. Remove the special tool, and install a new master cylinder rod seal in the brake booster.





9. Adjust the pushrod length as shown if the booster is removed.
10. Install the master cylinder.
11. After installation, inspect and adjust brake pedal height and freeplay.