Jeep Wagoneer/Commando/Cherokee 1984-1998

Booster Pump and Motor

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TESTING



See Figures 1 and 2

  1. Turn the ignition key to the ON position.
  2.  
  3. If the booster pump and motor does not run continuously, check the relay. If the pump and motor does run continuously, inspect the brake lines and fluid level carefully. If any fluid leaks are found, repair then add fluid as necessary.
  4.  
  5. Disengage the flat booster pump/motor wiring harness connector. Inspect the condition of the connector and repair as necessary.
  6.  



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Fig. Fig. 1: Location of the booster pump/motor, connectors and relay



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Fig. Fig. 2: Checking resistance of the booster pump and motor

  1. Using an ohmmeter, check the resistance between cavities B and C of the connector on the component side.
  2.  
  3. If the resistance measures below 10 ohms, replace the booster pump and motor assembly.
  4.  

Removal & Installation



See Figures 3, 4 and 5



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Fig. Fig. 3: View of the pump and motor assembly


CAUTION
This brake system uses hydraulic accumulators, which, when fully charged, contain brake fluid at very high pressure. Before disconnecting any components, hydraulic lines, hoses or fittings, be certain that the accumulator pressure is completely relieved. Failure to depressurize the system may result in personal injury and/or vehicle damage.

  1. Depressurize the brake system
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the strap holding the coolant reservoir bottle and move the bottle aside. The hoses may be left attached; moving the bottle allows better access.
  6.  
  7. Remove the bolts holding the 2-piece mounting bracket to the firewall and inner fender panels.
  8.  

  1. Move or rotate the bracket with the pump assembly to one side for access to the wiring and hoses. Disconnect the pump motor wiring harness from the engine harness.
  2.  
  3. Slowly loosen the high pressure line at the pump and allow any residual high pressure to bleed off. Wear eye protection and wrap the joint in a clean shop towel to suppress any spray. Disconnect the line from the pump.
  4.  
  5. Place a container or catch pan under the return line to the pump. Loosen the hose clamp and remove the line. Do not reuse the brake fluid which drains from the line.
  6.  
  7. Remove the pump/motor and bracket as a complete assembly.
  8.  
  9. Remove the screw holding the relay to the bracket. Remove the screws holding the pump and motor to the bracket and remove the bracket.
  10.  



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Fig. Fig. 4: Always wear eye protection when disconnecting the high pressure hose



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Fig. Fig. 5: Use a catch pan when disconnecting the supply/return line

To install:
  1. Position the pump assembly onto the bracket and install the assembly attaching screws. Attach the pump/motor to the mounting bracket and attach the pump relay to the mounting bracket.
  2.  
  3. Connect the high-pressure and return lines to the pump.
  4.  
  5. Connect the electrical harness from the pump to the engine harness.
  6.  
  7. Place the bracket with the pump/motor and relay in place and install the retaining bolts.
  8.  
  9. Inspect the high-pressure and return lines; make certain they are not kinked or touching the engine.
  10.  
  11. Fill the master cylinder to the MAX level.
  12.  
  13. Connect the negative battery cable.
  14.  
  15. Turn the ignition switch ON ; the pump should start running. Listen for a drop in pump rpm; this shows the pump is pressurizing the system. If there is no drop in pump rpm within 20 seconds, immediately shut the ignition OFF and check for hydraulic leaks.
  16.  

Severe pump damage will result if the pump runs without pressurizing the system for any length of time.

  1. Add fluid to the reservoir as necessary. Do not overfill.
  2.  
  3. Reposition and secure the coolant reservoir.
  4.  

 
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