Chrysler Full-Size Trucks 1997-2000 Repair Guide

Master Cylinder

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The master cylinder is a two-piece component with an aluminum cylinder body and a nylon reservoir. The reservoir can be removed and replaced, if need be. The cylinder, however, is not repairable and must be replaced as an assembly if it fails.



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Fig. Exploded view of typical master cylinder. Piston assembly can be removed after prying out the snap ring, but the unit is not rebuildable


CAUTION
Bleeding of four-wheel antilock brake systems require the use a dedicated scan tool. Lines should not be disconnected unless one is available.

REMOVAL & INSTALLATION




WARNING
Exercise care when removing and installing the master cylinder, combination valve and antilock valve connecting lines. The threads in the cylinder and valve fluid ports can be damaged easily. Use a flare nut wrench to loosen and tighten fittings and start all brake system fittings by hand to avoid crossthreading.


NOTE
Read the "Brake Hoses And Lines" section for useful hints and tips on brake line work.

  1. Place a container beneath the master cylinder brake line fittings to catch the fluid which will drip out when the fittings are removed.
  2.  


NOTE
Protect painted surfaces from contact with brake fluid; it will remove many types of paint, especially on plastics, in short order.

  1. Using a flare nut wrench, unscrew the fittings on the master cylinder.
  2.  
  3. Remove the nuts securing the master cylinder to the power brake booster. On some models, the combination valve bracket may have to be removed as well.
  4.  
  5. Remove the master cylinder.
  6.  
  7. Drain off the brake fluid.
  8.  

To install:

  1. If a new master cylinder is being installed, carry out the "Bench Bleeding" procedure first.
  2.  
  3. Install the master cylinder on the booster studs.
  4.  
  5. Fit the combination valve bracket on the booster stud, if so equipped.
  6.  
  7. Tighten the mounting nuts to 17 ft. lbs. (23 Nm).
  8.  
  9. Start the brake line fittings by hand. Move the lines as necessary to make sure the fittings engage the threads correctly. If resistance is felt, back them off and try again. Do NOT put a wrench on the fittings until you are sure they are correctly threaded.
  10.  
  11. Tighten the line fittings to 14 ft. lbs. (19 Nm). Do NOT over-tighten. Do NOT attempt to stop leaks by over-tightening the fittings. This is unlikely to help.
  12.  
  13. Add new fluid and bleed the brake system.
  14.  



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Fig. You have been warned



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Fig. Place a container beneath the fitting and use a flare nut wrench (arrow) to loosen it



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Fig. After disconnecting the brake lines, remove the nuts (arrows) to remove the master cylinder



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Fig. Removing the master cylinder

BENCH BLEEDING




WARNING
All new master cylinders should be bench bled prior to installation. Bleeding a new master cylinder on the vehicle is not a good idea. With air trapped inside, the master cylinder piston may bottom in the bore and possibly cause internal damage.

  1. Secure the master cylinder in a bench vise using soft jaws.
  2.  
  3. Remove the master cylinder reservoir cap.
  4.  
  5. Manufacture or purchase bleeding tubes and install them on the master cylinder as illustrated.
  6.  
  7. Fill the master cylinder reservoir with clean, fresh brake fluid until the level is within 0.25 in. (0.01mm) of the reservoir top.
  8.  


NOTE
Ensure the bleeding tubes are below the level of the brake fluid, otherwise air may get into the system making your bleeding efforts ineffective.

  1. Use a blunt-tipped rod (a long socket extension works well) to slowly depress the master cylinder piston. Make sure the piston travels full its full stroke.
  2.  
  3. As the piston is depressed, bubbles will come out of the bleeding tubes. Continue depressing and releasing the piston slowly until all bubbles cease.
  4.  
  5. Refill the master cylinder with fluid.
  6.  
  7. Remove the bleeding tubes.
  8.  
  9. Install the master cylinder reservoir cap.
  10.  
  11. Install the master cylinder on the vehicle and bleed the system.
  12.  



Click image to see an enlarged view

Fig. Bench bleeding the master cylinder using bleeding tubes

 
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