GM Celebrity/Century/Ciera/6000 1982-1996 Repair Guide

Master Cylinder

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REMOVAL & INSTALLATION



See Figures 1, 2 and 3

  1. For manual brakes, disconnect the master cylinder pushrod at the brake pedal inside the car. The pushrod is retained to the brake pedal by a clip. There is a washer under the clip, and a spring washer on the other side of the pushrod.
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Fig. Fig. 1: Exploded view of the master cylinder used on most models



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Fig. Fig. 2: Some later models use a slightly different master cylinder

  1. Unplug the electrical connector from the master cylinder.
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  3. Place a number of cloths or a container under the master cylinder to catch the brake fluid. Disconnect the brake tubes from the master cylinder, using a flare nut wrench, if one is available. Tape over or plug the open ends of the tubes.
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Fig. Fig. 3: Disconnect the brake tubes from the master cylinder with a flare nut wrench

Brake fluid eats paint. Wipe up any spilled fluid immediately, then flush the area with clean water.

  1. Remove the two nuts attaching the master cylinder to the booster or firewall.
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  3. Remove the master cylinder.
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To install:
  1. Attach the master cylinder to the firewall or the booster with the nuts. Tighten to 29 ft. lbs. (40 Nm) for 1982-84 models, 22 ft. lbs. (27 Nm) for 1985-88 models, and 20 ft. lbs. (27 Nm) 1989-96 models.
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  3. Reconnect the pushrod to the brake pedal.
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  5. Remove the tape from the lines and connect the lines to the master cylinder. Tighten to 12 ft. lbs. (17 Nm) for 1982-84 models, 18 ft. lbs. (24 Nm) for 1985-88 models, 24 ft. lbs. (32 Nm) for 1989-96 models. Connect the electrical lead.
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  7. Fill the master cylinder to the proper level with clean fresh brake fluid.
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  9. Bleed the brakes.
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  11. Recheck the fluid level and add fluid if needed.
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OVERHAUL



See Figures 4, 5, 6 and 7

This is a tedious, time consuming job. You can save yourself a lot of trouble by buying a rebuilt master cylinder from your dealer or parts supply house. The small difference in price between a rebuilding kit and a rebuilt part usually makes it more economical, in terms of time and work, to buy the rebuilt part.

  1. Remove the master cylinder from the vehicle.
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  3. Remove the reservoir cover and drain the fluid, inspect the cap for any cuts, cracks, nicks or deterioration.
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  5. Remove the pushrod and the rubber boot on non-power models.
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  7. Unbolt the proportioners and the failure warning switch from the side of the master cylinder body. Discard the O-rings found under the proportioners. Use new ones on installation. There may or may not be an O-ring under the original equipment failure warning switch. If there is, discard it. In either case, use a new O-ring upon assembly.
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  9. Clamp the master cylinder body in a vise, taking care not to crush it. Remove the snapring with a pair of snapring pliers or suitable tool.
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Fig. Fig. 4: A seal pick can be used to remove the snapring from the master cylinder

  1. The primary and secondary pistons can be removed by applying compressed air into one of the outlets at the end of the cylinder and plugging the other three outlets. The primary piston must be replaced as an assembly if the seals are bad. The secondary piston seals are replaceable. Install these new seals with the lips facing outwards.
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  3. Inspect the cylinder bore for scoring or corrosion. If any corrosion is evident, the master cylinder body must be replaced. Do not attempt to polish the bore with crocus cloth, sandpaper or anything else. The body is aluminum, polishing the bore won't work.
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  5. To remove the failure warning switch piston assembly, unfasten the Allen head plug from the end of the bore and withdraw the assembly with a pair of needlenose pliers. The switch piston assembly seals are replaceable.
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  7. The reservoir can be removed from the master cylinder if necessary. Clamp the body in a vise by its mounting flange. Use a prytool to remove the reservoir. When the reservoir is removed, remove the reservoir grommets and discard them. The quick take-up valves under the grommets are accessible after the retaining snaprings are removed. Use snapring pliers, no other tool will work without damaging the component.
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Fig. Fig. 5: When the master cylinder is completely disassembled, place the components on a clean workspace

To assemble:
  1. Clean all parts in denatured alcohol and allow to air dry. Do not use anything else to clean them, and do not wipe them dry with a rag, (which will leave bits of lint behind). Inspect all parts for corrosion or wear. Generally, it is best to replace all rubber parts whenever the master cylinder is disassembled and replace any metal part which shows any sign of wear or corrosion.
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Fig. Fig. 6: The seals on the secondary piston are replaceable

  1. Lubricate all parts with clean brake fluid before assembly.
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  3. Install the quick take-up valves into the master cylinder body and secure with the snaprings. Make sure the snaprings are properly seated in their grooves. Lubricate the new reservoir grommets with clean brake fluid and press them into the master cylinder.
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  5. Install the reservoir into the grommets by placing the reservoir on its lid and pressing the master cylinder body down onto it with a rocking motion.
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  7. Lubricate the switch piston assembly with clean brake fluid. Install new O-rings and retainers on the piston. Install the piston assembly into the master cylinder and secure with the plug, using a new O-ring on the plug. Tighten to 40-140 inch lbs. (5-16 Nm).
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  9. Assemble the new secondary piston seals onto the piston. Lubricate the parts with clean brake fluid, then install the spring, spring retainer and secondary piston into the cylinder. Install the primary piston, depress and install the lockring.
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  11. Install new O-rings on the proportioners and the failure warning switch. Install the proportioners and tighten to 18-30 ft. lbs. (25-40 Nm). Install the failure warning switch, then tighten to 15-50 inch lbs. (2-6 Nm).
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Fig. Fig. 7: Always install the components by hand before tightening them with a wrench

  1. Clamp the master cylinder body upright into a vise by one of the mounting flanges. Fill the reservoir with fresh brake fluid. Pump the piston with a dowel until fluid squirts from the outlet ports. Continue pumping until the expelled fluid is free of air bubbles.
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  3. Install the master cylinder, then tighten the nuts to 29 ft. lbs. (40 Nm) for 1982-84 models or 20-22 ft. lbs. (28-30 Nm) for 1985-96 models. Bleed the brake system, then check the system for proper operation. Do not move the car until a "hard" brake pedal is obtained and the brake system has been thoroughly checked for soundness.
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