REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6 and 7
- Apply the parking brakes and block the drive wheels.
- Use a line wrench to loosen and disconnect the hydraulic lines from the master cylinder. Immediately plug the lines to prevent system contamination or excessive fluid loss.
- If equipped with non-power brakes, disconnect the pushrod from the brake pedal.
- Remove the master cylinder attachment nuts, then separate the combination valve/bracket from the master cylinder.
- Remove the master cylinder and, as equipped, the gasket and/or rubber boot from the vehicle.
In order to ease installation, bench bleed the master cylinder before installation:
- Plug the master cylinder outlet ports. This can be done using rubber or plastic plugs or, more effectively, using a single length of brake line with appropriately sized flares/flare nuts on each end.
- Mount the cylinder in a soft-jawed vise with the front end tilted slightly downward.
- Fill the reservoir with clean brake fluid, then use a tool with a smooth rounded end (such as a wooden dowel or pencil eraser) to stroke the primary piston about 1 in. (21mm) several times. As air is bled from the cylinder, the primary piston will no longer travel the full distance.
- Reposition the master cylinder in the vise with the front end tilted slightly up, then continue stroking the primary piston to further bleed air.
- Reposition the master cylinder so it is level, then loosen the plugs one at a time and push the piston into the bore forcing air from the cylinder. DO NOT allow the piston to return with the plugs loosened or air will be drawn back into the master cylinder.
- Make sure the plugs are tightly sealed, then check and refill the reservoir.
- Position the master cylinder to the cowl or brake booster (as applicable), then reposition the combination valve bracket over the studs.
Install the master cylinder/combination valve bracket retaining nuts and tighten as follows:
- Vehicles through 1553 except Typhoon - 20 ft. lbs. (23 Nm).
- Typhoon - 9 ft. lbs. (9 Nm).
- Working on one line at a time, remove the plugs and quickly connect the brake lines to the master cylinder. Tighten each of the line nuts to 20 ft. lbs. (23 Nm).
If equipped with manual brakes, be sure to reconnect the pushrod to the brake pedal.
- Refill the master cylinder with clean brake fluid, then properly bleed the hydraulic brake system and check the brake pedal travel.
- When all service is finished, remove the blocks from the drive wheels.
See Figures 8, 9 and 10
- Remove the master cylinder from the vehicle.
- Clamp the mounting flange of the master cylinder in a vise so the reservoir is facing 1 side.
- Some early model and most late model vehicles should be equipped with a removable master cylinder reservoir. If so, carefully pry the reservoir from the top of the cylinder assembly. Remove the reservoir grommets.
- At the rear of the master cylinder, depress the primary piston and remove the lockring.
- Grasp and withdraw the primary piston assembly from the cylinder bore. If necessary, use a SMALL amount of air pressure to push the piston out of the bore to where it can be grasped and pulled out.
- Block the rear outlet hole, then apply a SMALL amount of compressed air into the front outlet hole in order to remove the secondary piston from the master cylinder. If compressed air is not available, a hooked wire may be used to pull out the secondary piston, but you must be EXTREMELY careful not to score or damage the cylinder bore if this method is used. In some cases the secondary piston can be dislodged by gently striking the open end of the master cylinder assembly on a block of wood.
- Remove the seals, spring retainer and spring from the secondary piston.
DO NOT attempt to remove the quick take-up valve from the master cylinder body; the valve is not serviceable separately.
- Using denatured alcohol, clean and blow dry all of the master cylinder parts.
- Inspect the master cylinder bore for corrosion or scratches; if damaged, replace the master cylinder with a new one.
Be sure to replace ALL grommets and seals. During assembly the grommets, seals and cylinder bore should be lubricated with clean brake fluid.
- Install the spring, spring retainer and seals to the secondary piston assembly.
- Carefully insert and seat the secondary piston assembly.
- Install the primary piston assembly.
- Depress and hold the primary piston, then install the lockring.
- Install the reservoir grommets, then position the reservoir(s) on a flat, hard surface such as a block or blocks of wood. Carefully press the master cylinder onto the reservoirs, using a rocking motion.
- Install the new diaphragm(s) onto the reservoir cover(s).
- Bench bleed and install the master cylinder to the vehicle.
- Properly bleed the hydraulic brake system.