GM 91171392
Brake Booster

You must first take off the brake modulator assembly when replacing your vacuum Brake Booster and then remove the master cylinder. Disengage the hose from the booster by a hose clamp before removing the pin and bolt at the clevis end of the push rod. Unfasten the Brake Booster assembly from the bulkhead by removing its four mounting nuts first then take off the push rod clevis from the Brake Pedal. To adjust the booster correctly set the piston rod using the Brake Booster piston rod height gauge tool j 39567 with the master cylinder piston. Push the booster piston rod several times to verify the reaction disc positioned correctly on the part. Fit the j 39567 gauge onto the master cylinder and push its pin until it touches the master cylinder piston . Place the upside-down gauge j 39567 on the booster assembly to test if the booster piston rod touches the gauge without any space between them (0 mm). Turn the adjusting nut on the booster piston rod to alter its length so that test specifications get met. Put the push rod clevis into place when the measurement between 99.5 and 100.5 millimeters (3.92 and 3.96 inches) is met. Tighten the push rod clevis locknut to a torque of 25 nm (18 ft. Lbs.). Put silicone grease on the master cylinder piston before placing the booster assembly onto the bulkhead but do not tighten its mounting nuts yet. Place the brake push rod clevis over the Brake Pedal and fasten it with the clevis pin and cotter pin and secure the booster assembly fixings at 13 nm (115 inch lbs.). Connect the hose to the booster unit through a hose clamp then put back the brake modulator assembly (when present with ABS) and master cylinder.