GM Caprice 1990-1993 Repair Guide

Master Cylinder

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REMOVAL & INSTALLATION



See Figure 1



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Fig. Fig. 1: Master cylinder replacement

Be sure to clean the area where the master cylinder is mounted, before beginning removal.

  1. Disconnect and cap or plug hydraulic lines to prevent fluid contamination or loss.
  2.  
  3. Remove the attaching nuts.
  4.  
  5. If the combination valve bracket is mounted over the master cylinder on the power brake booster studs, pull the bracket from the studs and reposition it aside.
  6.  
  7. Remove the master cylinder.
  8.  

To install:
  1. Install the master cylinder on the power booster studs.
  2.  
  3. If applicable, install the combination valve bracket on the power booster studs.
  4.  
  5. Install the attaching nuts and tighten to 20 ft. lbs. (27 Nm) for all except 1991 vehicles or tighten to 15 ft. lbs. (21 Nm) for 1991 vehicles only.
  6.  
  7. Unplug hydraulic lines, attach to the master cylinder and tighten to 24 ft. lbs. (32 Nm).
  8.  
  9. Fill with approved brake fluid and bleed system.
  10.  

OVERHAUL



See Figures 2, 3 and 4



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Fig. Fig. 2: Master cylinder exploded view



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Fig. Fig. 3: Removing the master cylinder reservoir



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Fig. Fig. 4: Install the master cylinder-to reservoir with a rocking motion

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 reservoir cover and diaphragm. Discard any brake fluid in the reservoir.
  2.  
  3. Inspect the reservoir cover and diaphragm for cuts, cracks, or deformation. Replace any defective parts.
  4.  
  5. Depress the primary piston and remove the lock ring.
  6.  
  7. Direct compressed air into the outlet at the blind end of the bore and plug the other outlet to remove primary and secondary piston.
  8.  
  9. Remove the spring retainer and seals from the secondary piston.
  10.  
  11. Clamp the master cylinder in a vise. Do not clamp it on the master cylinder body. Using a pry bar, remove the reservoir.
  12.  
  13. Do not attempt to remove the quick take-up valve from the body. This valve is not serviced separately.
  14.  
  15. Remove the reservoir grommets.
  16.  
  17. Inspect the master cylinder bore for corrosion. If corroded, replace the master cylinder. Do not use any abrasive on the bore.
  18.  
  19. Reassemble, using new seals and grommets. Lubricate all parts with brake fluid.
  20.  
  21. Install the reservoir grommets.
  22.  
  23. Install the reservoir.
  24.  
  25. Install the spring retainer and seals from the secondary piston.
  26.  
  27. Install primary and secondary piston.
  28.  
  29. Depress the primary piston and install the lock ring.
  30.  
  31. Fill with brake fluid. Install the reservoir cover and diaphragm.
  32.  
  33. Bleed brake system.
  34.  

 
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