REMOVAL & INSTALLATION
Be careful not to spill brake fluid on the painted surfaces of the vehicle, as it will damage the paint.
- Unfasten the hydraulic lines from the master cylinder.
- Disconnect the hydraulic fluid pressure differential switch wiring. On models with fluid level sensors, also disconnect the fluid level sensor wiring.
- Loosen the master cylinder reservoir mounting bolts.
- On models with manual brakes, unfasten the master cylinder securing bolts and the clevis pin from the brake pedal, then remove the master cylinder. On models with power brakes, unfasten the nuts and remove the master cylinder assembly from the power brake unit.
Install the master cylinder in reverse order of removal and note the following:
Many models have an UP mark on the cylinder boot; make sure it is in the correct position.
When replacing the the master cylinder, it is best to BENCH BLEED the master cylinder before installing it to the vehicle. Mount the master cylinder into a soft-jawed vise or suitable equivalent, so as not to damage the cylinder. Fill the cylinder to the correct level with new DOT 3 type brake fluid. Block off all the outer brake line holes but one, then position a long wooden dowel in the bore to actuate the brake master cylinder. Pump the brake master cylinder 3 or 4 times (push in and out with the dowel) until brake fluid is released and no air is in the brake fluid. Repeat this procedure until all brake fluid is released from every hole and no air is expelled.
See Figure 1
Because of the importance of the master cylinder, replacement (rather than overhaul) is recommended if it is worn or damaged.
- Place the cylinder securely in a soft-jawed vise or suitable equivalent. Remove the reservoir caps and floats. Unscrew the bolts which secure the reservoir(s) to the main body.
- Remove the pressure differential warning switch assembly. Working from the rear of the cylinder, remove the boot, snapring, stop washer, primary piston, spacer, cylinder cup, spring retainer, and spring, in that order.
- Remove the end plug and gasket from the front of the cylinder (if equipped), then remove the front piston stop bolt from underneath. Pull out the spring, retainer, secondary piston, spacer, and cylinder cup.
- Remove the two outlet fittings, washers, check valves and springs.
- Remove the piston cups from their seats only if they are to be replaced.
- Wash all parts in clean brake fluid, then dry them with compressed air (if available). Do not dry parts with a shop rag, as this can deposit lint and dirt particles inside the assembled master cylinder. Inspect the cylinder bore for wear, scuff marks, or nicks. Cylinders may be honed slightly, but the limit is 0.006 in. (0.15mm).
- Replace any worn or damaged parts. Coat all parts with clean brake fluid, then reassemble the master cylinder.
Absolute cleanliness is essential!
- Install the master cylinder.
- Bleed the hydraulic system after the master cylinder is installed.