REMOVAL & INSTALLATION
See Figures 1, 2 and 3
- Disconnect and plug the brake lines.
- Disconnect the wires from the stoplight switch.
- Disconnect the master cylinder pushrod at the brake pedal (non-power brakes only), remove all attaching bolts and nuts and lift the assembly from the vehicle.
- Position the master cylinder and install the mounting bolts. Torque the mounting bolts to 30 ft. lbs. on 1971-86 models.
- Connect the pushrod on non-power brakes and connect the wiring.
- Connect the brake lines and bleed the master cylinder and brake system.
See Figures 4 through 161971-75 Models
- Remove the filler cap and empty all the fluid.
- The stop light switch and primary piston stop, located in the stop light switch outlet hole, must be removed before removing the snapring from the piston bore. Remove the snapring, pushrod assembly and the primary and secondary piston assemblies. Air pressure applied in the piston stop hole will help facilitate the removal of the secondary piston assembly.
- The residual check valves are located under the front and rear fluid outlet tube seats.
- The tube seats must be removed with self tapping screws to permit the removal of the check valves. Screw the self-tapping screws into the tube seats and place two screw driver tips under the screw head and force the screw upward.
- Remove the expander in the rear secondary cup, secondary cups, return spring cup protector, primary cup, and washer from the secondary piston.
- Immerse all of the metal parts in clean brake fluid and clean them. Use an air hose to blow out dirt and cleaning solvent from recesses and internal passages.
- After cleaning, place all of the parts on clean paper or in a clean pan.
- Inspect all parts for damage or excessive wear. Replace any damaged, worn, or chipped parts. Inspect the hydraulic cylinder bore for signs of scoring, rust, pitting, or etching. Any of these will require replacement of the hydraulic cylinder.
- Prior to assembling the master cylinder, dip all of the components in clean brake fluid and place them on clean paper or in a clean pan.
- Install the primary cup washer, primary cup, cup protector, and return spring in the secondary position.
- Install the piston cups in the double groove end of the secondary piston, so the flat side of the cups face each other (lip of the cups away from each other). Install the cup expander in the lip groove of the end cup.
- Coat the cylinder bore and piston assemblies with clean brake fluid before installing any parts in the cylinder.
- Install the secondary piston assembly first and then the primary piston.
- Install the pushrod assembly, which includes the pushrod, boot, and rod retainer, and secure with the snapring. Install the primary piston stop and stop light switch.
- Place new rubber check valves over the check valve springs and install in the outlet holes, spring first.
- Install the tube seats, flat side toward the check valve, and press in with tube nuts or the master cylinder brake tube nuts.
- Before the master cylinder is installed on the vehicle it must be bled. Support the cylinder assembly in a vise and fill both fluid reservoirs with brake fluid.
- Loosely install a plug in each outlet of the cylinder. Depress the push rod several times until air bubbles cease to appear in the brake fluid.
- Tighten the plugs and attempt to depress the piston. The piston travel should be restricted after all of the air is expelled.
- Install the master cylinder in the vehicle and bleed all the hydraulic lines at the wheel cylinders.
- Remove the master cylinder from the vehicle and remove the cover and diaphragm seal. Drain the brake fluid from the reservoir and mount it in a vise.
- With non-power brakes, slide the boot back on the pushrod. Push the pushrod in and unseat the primary piston snapring. Remove the pushrod, boot, snapring, and pushrod retainer as an assembly. With power brakes, push the primary piston in with a wooden dowel and remove the piston snapring.
- Remove the primary and secondary piston assemblies. Air pressure applied through the piston stop hole will help in the removal of the secondary piston.
- Clamp the primary piston pushrod in a vise, with the brake pedal eyelet facing downward and the rear face of the primary piston positioned just above the jaws of the vise.
- Remove the rubber insert from the primary piston and discard it. NEVER ATTEMPT TO REUSE THIS INSERT! A REPLACEMENT INSERT MUST BE OBTAINED!!
- Remove the piston seal and piston cups from the secondary piston. It is not necessary to disassemble the primary piston because a new complete primary piston assembly is supplied in the rebuilding kit.
- Clean and inspect the master cylinder. Replace the master cylinder body if the bore is severely scored, corroded, or pitted, cracked, porous, or is otherwise damaged. Check the by-pass and compensator ports to make sure that they are open and not plugged or dirty. Use brake fluid and air pressure to open these passages. Do not use wire.
Use only clean brake fluid or an approved cleaning solvent to wash the master cylinder. Do not use any solvent containing mineral oil such as gasoline, kerosene, alcohol, or carbon tetrachloride. Mineral oil harms rubber components.
Check the tube seats in the outlet ports. Replace the seats only if they are cracked, scored, cocked in the bore, or loose. Replace the tube seats as follows:
- Enlarge the hole in the tube seat with a 13 / 64 in. drill bit.
- Place a flat washer on each outlet port and thread a 1 / 4 -20 x 3 / 4 in. long screw into the seat.
- Tighten the screw until the seat is loosened.
- Remove the seat, screw, and washer. Flush any metal chips away with brake fluid and compressed air.
- Install the replacement tube seats, if removed, using spare tube fitting nuts to press the seats into place. Be careful that the seats don't become cocked during installation. Make sure that the seats are bottomed. Remove the tube fitting nuts and check for burrs or chips. Rinse the master cylinder in brake fluid and blow out all passages with compressed air.
- Install the piston cups on the secondary piston. The piston cup installed in the groove at the end of the piston should have its lip facing away from the piston. Install the next cup so that its lip faces the piston.
- Install the seal protector, piston seal, spring retainer, and return spring on the secondary piston. Install the piston seal so that its lip faces the interior of the master cylinder bore when the assembly is installed. Make sure that the return spring seats against the retainer and that the retainer is located inside the lip of the piston seal.
- Lubricate the master cylinder bore and secondary piston seal and cups with brake fluid and install the secondary piston assembly in the cylinder bore.
- Lubricate the seals on the primary piston assembly with brake fluid and install the assembly in the master cylinder bore.
- With power brakes, push the primary piston inward with a wooden bowel and install the retaining snapring in the groove of the master cylinder bore.
- With non-power brakes, install the pushrod, pushrod retainer, and boot. Push in and install the piston snapring.
- Install the diaphragm seal on the master cylinder cover.
- Install the master cylinder in the vehicle. Bleed the system.