GM Full Size Vans 1987-1997 Repair Guide

Master Cylinder

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REMOVAL & INSTALLATION



See Figures 1 through 4



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Fig. Fig. 1: Typical master cylinder mountings


WARNING
Clean any master cylinder parts in alcohol or brake fluid. Never use mineral based cleaning solvents such as gasoline, kerosene, carbon tetrachloride, acetone, or paint thinner as these will destroy rubber parts. Do not allow brake fluid to spill on the vehicle's finish, it will remove the paint. Flush the area with water.



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Fig. Fig. 2: Use a suction device to remove about a third of the brake fluid from the master cylinder

  1. Using a clean cloth, wipe the master cylinder and its lines to remove excess dirt and then place cloths under the unit to absorb spilled fluid.
  2.  
  3. Remove the hydraulic lines from the master cylinder and plug the outlets to prevent the entrance of foreign material. On vans with ABS, disconnect the lines at the isolation/dump valve.
  4.  
  5. Remove the master cylinder attaching bolts or, on vans with ABS, the attaching bolts from the isolation/dump valve, and remove the master cylinder from the brake booster, or, on vans with manual brakes, the firewall.
  6.  



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Fig. Fig. 3: Place a rag under the line wrench to help minimize spillage when disconnecting the brake lines



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Fig. Fig. 4: Loosen the master cylinder mounting nuts and remove the master cylinder


WARNING
On vans with ABS, never let brake fluid or your skin touch the ECU electrical connections! Also, never let the isolation/dump valve hang by its wiring!

To install:
  1. Position the master cylinder or, on vans with ABS the master cylinder and isolation/dump valve, on the booster or firewall. Tighten the nuts to 20 ft. lbs. (27 Nm) on 1987-93 models and 27 ft. lbs. (36 Nm) on 1994-97 models.
  2.  
  3. Connect the brake lines and tighten them to 13 ft. lbs. (17 Nm). Fill the master cylinder reservoirs to the proper levels.
  4.  
  5. Bleed the brakes master cylinder, then the complete system.
  6.  

 
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