Jeep Wagoneer/Commando/Cherokee 1957-1983 Repair Information

Master Cylinder

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See Figure 1

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Fig. Fig. 1: Place a rag under the line wrench to help minimize spillage when disconnecting the brake lines

REMOVAL & INSTALLATION FC Series



The master cylinder is located under the instrument panel, in front of the steering column. Before removing the master cylinder, place rags under it to catch any spilled fluid. Brake fluid is a great paint remover.

  1. Disconnect and cap the brake lines at the master cylinder.
  2.  
  3. Unbolt and remove the master cylinder.
  4.  


WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded.

  1. Prior to installation, fill the master cylinder and operate the pushrod until fluid squirts from the ports.
  2.  
  3. Install the master cylinder and fill it to within 1 / 2 in. of the cap.
  4.  

All except FC Series

  1. Disconnect and plug the brake lines.
  2.  
  3. Disconnect the wires from the stoplight switch.
  4.  
  5. Remove all attaching bolts and nuts, and lift the assembly from the vehicle.
  6.  


WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded.

  1. Prior to installation, fill the master cylinder and operate the pushrod until fluid squirts from the ports.
  2.  
  3. Installation is the reverse of removal. Torque the mounting nuts to 30 ft. lb. on all 1962-83 models. Bleed the brake system.
  4.  

OVERHAUL



Do not use any type of mineral oil, gasoline or kerosene to clean any part of any hydraulic brake system. These fluids will cause rubber parts to soften, swell, and distort, resulting in failure. Use only clean brake fluid or alcohol.

FC Series See Figure 2

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Fig. Fig. 2: Exploded view of the master cylinder components FC models

  1. Remove the fitting connections and gaskets.
  2.  
  3. Empty all fluid from the cylinder.
  4.  
  5. Remove the lockwire, stop plate and piston.
  6.  
  7. Remove the primary cup and piston spring.
  8.  
  9. Remove the valve and valve seat.
  10.  
  11. Thoroughly clean and inspect all parts. Rebuilding kits usually contain all necessary parts. Inspect the cylinder bore. If it is at all worn or scored, it should be honed. If honing cannot remove all traces of imperfections, the master cylinder should be replaced. After honing, check the piston-to-bore clearance with a feeler gauge. Clearance should be 0.001-0.005 in. If clearance is excessive, replace the unit.
  12.  


WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded.

  1. Assembly is the reverse of disassembly. Prior to assembly, coat all parts with clean brake fluid. Note that the flat surface of the valve seat faces the valve, and the flat side of the primary cup faces the piston.
  2.  

Jeepster/Commando


WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded. See Figure 3

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Fig. Fig. 3: Exploded view of a dual master cylinders components Jeepster/Commando models


  1. Remove the filler cap and empty all the fluid.
  2.  
  3. The stop light switch and primary piston stop, located in the stop light switch outlet hole, must be removed before removing the snap right from the piston bore. Remove the snapring, pushrod assembly and the primary and secondary piston assemblies. Air pressure applied in the piston stop hole will help facilitate the removal of the secondary piston assembly.
  4.  
  5. The residual check valves are located under the front and rear fluid outlet tube seats.
  6.  
  7. The tube seats must be removed with self-tapping screws to permit the removal of the check valves. Screws the self-tapping screws into the tube seats and place two screwdriver tips under the screw head and force the screw upward.
  8.  
  9. Remove the expander in the rear secondary cup, secondary cups, return springs, cup protector, primary cup, and washer from the secondary piston.
  10.  
  11. Immerse all of the metal parts in clean brake fluid and clean them. Use an air hose to blow out dirt and cleaning solvent from recesses and internal passages.
  12.  
  13. After cleaning, place all of the parts on clean paper in a clean pan.
  14.  
  15. Inspect all parts for damage or excessive wear. Replace any damaged, worn, or chipped parts. Inspect the hydraulic cylinder bore for signs of scoring, rust, pitting, or etching. Any of these will require replacement of the hydraulic cylinder.
  16.  
  17. Prior to assembling the master cylinder, dip all of the components in clean brake fluid and place them on clean paper or in a clean pan.
  18.  
  19. Install the primary cup washer, primary cup, cup protector, and return spring on the secondary piston.
  20.  
  21. Install the piston cups in the double groove end of the secondary piston, so the flat side of the cups face each other (lip of the cups away from each other). Install the cup expander in the lip groove of the end cup.
  22.  
  23. Coat the cylinder bore and piston assemblies with clean brake fluid before installing any parts in the cylinder.
  24.  
  25. Install the secondary piston assembly first and then the primary piston.
  26.  
  27. Install the pushrod assembly, which includes the pushrod, boot, and rod retainer, and secure with the snapring. Install the primary piston stop and stop light switch.
  28.  
  29. Place new rubber check valves over the check valve springs and install in the outlet holes, spring first.
  30.  
  31. Install the tube seats, flat side toward the check valve, and press in with tube nuts or the master cylinder brake tube nuts.
  32.  
  33. Before the master cylinder is installed on the vehicle, it must be bled. Support the cylinder assembly in a vise and fill both fluid reservoirs with brake fluid.
  34.  
  35. Loosely install a plug in each outlet of the cylinder. Depress the pushrod several times until air bubbles cease to appear in the brake fluid.
  36.  
  37. Tighten the plugs and attempt to depress the piston. The piston travel should be restricted after all of the air is expelled.
  38.  
  39. Install the master cylinder in the vehicle and bleed all the hydraulic lines at the wheel cylinders.
  40.  

1962-69 Wagoneer and J-Series Truck


WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded. See Figure 4

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Fig. Fig. 4: Common master cylinder components 1962-69 Wagoneer and J-series truck models


  1. Remove the fitting connections and gaskets.
  2.  
  3. Empty all fluid from the cylinder.
  4.  
  5. Remove the lockwire, stop plate and piston.
  6.  
  7. Remove the primary cup and piston spring.
  8.  
  9. Remove the valve and valve seat.
  10.  
  11. Thoroughly clean and inspect all parts. Rebuilding kits usually contain all necessary parts. Inspect the cylinder bore. If it is at all worn or scored, it should be honed. If honing cannot remove all traces of imperfections, the master cylinder should be replaced. After honing, check the piston-to-bore clearance with a feeler gauge. Clearance should be 0.001-0.005 in. If clearance is excessive, replace the unit.
  12.  
  13. Assembly is the reverse of disassembly. Prior to assembly, coat all parts with clean brake fluid. Note that the flat surface of the valve seat faces the valve, and the flat side of the primary cup faces the piston.
  14.  

1970-80 Wagoneer, Cherokee and J-Series Truck See Figures 5 and 6

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Fig. Fig. 5: Exploded view of the master cylinder used on 1970-80 Wagoneer, Cherokee and J-series truck models



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Fig. Fig. 6: Remove the tube seats from the master cylinder with a prytool


WARNING
Clean, high quality brake fluid is essential to the safe and proper operation of the brake system. You should always buy the highest quality brake fluid that is available. If the brake fluid becomes contaminated, drain and flush the system, then refill the master cylinder with new fluid. Never reuse any brake fluid. Any brake fluid that is removed from the system should be discarded.

  1. Remove the cover, drain the cylinder and mount it in a vise.
  2.  
  3. On vehicles with non-power brakes, remove the boot, pushrod and pushrod retainer.
  4.  
  5. Remove the secondary piston stop from the bottom of the unit with a 5 / 16 in. socket.
  6.  
  7. Using a drift or punch, push the primary piston inward and remove the snapring from its groove.
  8.  
  9. Remove the primary and secondary piston assemblies. It may be necessary to apply air pressure through the piston stop hole to free the secondary piston.
  10.  
  11. Inspect all parts after a thorough cleaning. Inspect the tube seats in the outlet ports. Replace the seats only if they are cracked, cocked or loose. To replace a seat, thread a 6-32x 5 / 8 in. long self tapping screw into the tube seat. Pry out the seat using two small prybars on the screw.

    Rebuilding kits contain all the necessary parts. Replace all parts with those supplied in the kit. Never reuse a rubber part or any part that appears worn or damaged.
     
    Imperfections in the bore may be removed by honing. If any imperfection remains after honing, replace the unit.
     

  12.  

  1. Assembly is the reverse of disassembly. Prior to assembly, coat all parts with clean brake fluid. Note the following:
    1. The piston cup installed in the groove at the end of the piston should have its lip facing away from the piston.
    2.  
    3. Install the secondary piston seal so that the lip faces the interior of the unit.
    4.  
    5. Be sure that the return spring seats against the retainer and is seated inside the lip of the seal.
    6.  
    7. When installing the piston assemblies, be certain that the secondary piston is pushed back far enough to clear the piston stop. Tighten the stop to 33 in. lb.
    8.  

  2.  

1981-83 Wagoneer and Cherokee and J-Series Truck See Figures 7 and 8

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Fig. Fig. 7: Exploded view of the master cylinder used on 1981 models



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Fig. Fig. 8: Exploded view of a master cylinder and its components 1982-83 Wagoneer, Cherokee and J-series truck models

  1. Remove the cover, drain the cylinder and mount it in a vise.
  2.  
  3. Remove the reservoir from the master cylinder body by prying it off with a small prybar.
  4.  
  5. Using a drift or punch, push the primary piston inward and remove the snapring from its groove.
  6.  
  7. Remove the primary and secondary piston assemblies. It may be necessary to apply air pressure through the piston stop hole to free the secondary piston.
  8.  
  9. Inspect all parts after a thorough cleaning. Inspect the tube seats in the outlet ports. Replace the seats only if they are cracked, cocked or loose. To replace a seat, thread a 6-32x 5 / 8 in. long self tapping screw into the tube seat. Pry out the seat using two small prybars on the screw.
  10.  



Rebuilding kits contain all the necessary parts. Replace all parts with those supplied in the kit. Never reuse a rubber part or any part that appears worn or damaged.
 
Imperfections in the bore may be removed by honing. If any imperfection remains after honing, replace the unit.
 

  1. Assembly is the reverse of disassembly. Prior to assembly, coat all parts with clean brake fluid. Note the following:
    1. The piston cup installed in the groove at the end of the piston should have its lip facing away from the piston.
    2.  
    3. Install the secondary piston seal so that the lip faces the interior of the unit.
    4.  
    5. Be sure that the return spring seats against the retainer and is seated inside the lip of the seal.
    6.  

  2.  

  1. Lay the reservoir upside down on a flat, hard surface and press the master cylinder onto it with a rocking motion.
  2.  

 
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