Ram B1500, B2500, B3500, 1999-2003

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.

Fluid Recommendations & Fill




NOTE
When making additions of fluid, use only fresh, uncontaminated brake fluid meeting or exceeding DOT 3 standards. Be careful not to spill any brake fluid on painted surfaces, because it will damage the paint. Do NOT allow the brake fluid to contact any plastic parts like grill or trim. It may damage some types of plastic. Do NOT allow the fluid container or brake fluid reservoir to remain open any longer than necessary.


WARNING
Do NOT use old brake fluid that has been sitting on your shelf for any length of time, even if you think the bottle cap was tight. Brake fluid is hygroscopic, meaning it acts like a sponge to soak up water vapor from the air. Old brake fluid is likely to be water-contaminated which will have a detrimental affect on your braking system, reducing effectiveness and causing corrosion.



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Fig. Fill the brake master cylinder reservoir to the correct level with FRESH brake fluid

Level Check



The master cylinder reservoir is located on the left side of the firewall. Several different types are used. Older styles have a metal cap secured by a wire bale. Other versions use screw-on caps or a one-piece snap-on plastic cap.

If an inspection window is provided, check fluid level relative to the mark(s). Add fluid if level is at or near the "MIN" mark.

On master cylinders with screw-on caps, the level should reach the bottom of the filler hole ring.

On older style master cylinders (one-piece metal caps), the level should be about 1 / 4 in. below the reservoir lip.

Before removing a reservoir cap, clean all dirt away from the top of the master cylinder



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Fig. Brake master cylinder with one-piece metal cap secured by wire bale



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Fig. Brake master cylinder with screw-on caps. Fluid compartments are independent: be sure to check both



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Fig. Brake master cylinder with level inspection window



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Fig. Clean the area around the cap before removal


NOTE
Any sudden drop in fluid level probably indicates a leak in the system which must be investigated immediately.

There is a rubber diaphragm in the top of the master cylinder cap. As the fluid level falls in the reservoir due to normal brake wear, the diaphragm takes up the space. This is to keep air out of the system due to sloshing as well as to prevent leaks. Make sure to inspect this cap for any tears or cracks, it will require replacement if any damage has occurred.

After refilling the master cylinder to the proper level (using the proper brake fluid), but before installing the cap, be sure to fold the rubber diaphragm up into the cap. Then install the cap in the reservoir and tighten the retaining bolt or snap the retaining clip into place.

If the level of the brake fluid is less than half the volume of the reservoir, it is advised that you check the brake system for leaks. Leaks in the hydraulic brake system most commonly occur at the wheel.

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

 
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