Brake Pedal Assy: Adjustments

Fig. 12 Typical brake pedal adjustment. Chevrolet Nova:

Brake Pedal
1. With engine running and brake pedal in rest position, measure distance between face of pedal and floor mat, Fig. 12.
2. If distance is not 5.79---6.18 inches, adjust pedal height as follows:
a. Remove left lower instrument panel trim section and air duct.
b. Loosen stop lamp switch sufficiently to gain clearance for pedal adjustment.
c. Loosen locknut and rotate pedal pushrod as needed to obtain specified pedal height, then tighten locknut.
d. Adjust position of brake light switch so that plunger lightly contacts pedal stopper and brake lamps are off when pedal is released.
e. Check pedal free travel.
3. With engine stopped, depress brake pedal several times to ensure that there is no vacuum pressure in booster.
4. Release pedal, then press pedal down until the beginning of resistance is felt, measuring the pedal travel. Pedal free travel is the amount that the brake booster air valve is moved by the pedal pushrod.
5. If pedal travel is not .12---.24 inch, adjust pedal freeplay as follows:
a. Adjust pedal free travel by loosening locknut and rotating pedal pushrod.
b. Ensure that brake lamp switch and pedal height are properly adjusted, the start engine and confirm that free travel still exists.
c. Check pedal reserve distance.
6. Release parking brake and start engine.
7. Depress brake pedal and measure distance from face of pedal to floor mat. If pedal reserve distance is not more than 2.56 inch with an applied force of 110.2 lbs., check and repair brake system as needed.

Fig. 13 Adjusting pushrod gauge on master cylinder. Chevrolet Nova:

Fig. 14 Checking pushrod height. Chevrolet Nova:

Booster Pushrod
The following adjustment procedure is performed with the brake booster removed, using gauge J-34873-A or equivalent. This procedure should produce a clearance of .004---.020 inch between booster pushrod and master cylinder piston, with idling vacuum applied to booster.
1. Position gauge on rear of master cylinder, with gasket in place, Fig. 13.
2. Lower gauge pin until pin lightly contacts master cylinder piston, then secure position of gauge pin.
3. Invert gauge and position gauge over pushrod on booster, Fig.14.
4. Adjust length of pushrod so that tip of pushrod lightly contacts head of gauge pin with gauge resting on booster shell.