Pacifica, 2003-2005

Hydraulic Control Unit

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Removal & Installation



Mk25 ABS Sytem

The Hydraulic Control Unit (HCU) is mounted to the CAB as part of the Integrate Control Unit (ICU). The HCU controls the flow of brake fluid to the brakes using a series of valves and accumulators. A pump/motor is mounted on the HCU to supply build pressure to the brakes during an ABS stop.

  1. Disconnect and isolate the negative battery cable.
    WARNING
    The vacuum in power brake booster must be pumped down (removed) before removing master cylinder from power brake booster. This is necessary to prevent power brake booster from sucking in any contamination as master cylinder is removed. This can be done simply by pumping brake pedal, with vehicle's engine not running, until a firm feeling brake pedal is achieved.

  2.  
  3. With engine not running, pump brake pedal until a firm pedal is achieved (4-5 strokes).
  4.  
  5. Remove nuts fastening coolant recovery bottle in place and reposition bottle with hoses attached out of way.
    WARNING
    Before removing master cylinder from power brake vacuum booster, master cylinder and vacuum booster must be thoroughly cleaned. This must be done to prevent dirt particles from falling into power brake vacuum booster.

  6.  
  7. Thoroughly clean all surfaces of brake fluid reservoir and master cylinder, paying special attention to area where master cylinder attaches to power brake booster. Use only Mopar® Brake Parts Cleaner or equivalent.
  8.  
  9. Disconnect wiring harness connector from brake fluid level switch in master cylinder brake fluid reservoir.
  10.  
  11. Disconnect primary and secondary brake tubes coming from master cylinder at ABS ICU. Cap off brake tubes and install sealing plugs in open brake tube outlet ports of ICU.
  12.  
  13. Remove two nuts attaching master cylinder to power brake booster.
  14.  
  15. Slide master cylinder straight out of power brake booster.
    WARNING
    The seal on rear of master cylinder is used to create seal for holding vacuum in power brake vacuum booster. Vacuum seal on master cylinder MUST be replaced whenever master cylinder is removed from power brake vacuum booster.



    Click image to see an enlarged view

    Fig. Intake manifold (1), booster vacuum hose (2), power brake booster (3), master cylinder (4), primary brake tube (5), secondary brake tube (6), ABS ICU (7), master cylinder mounting nuts (8)

    Intake manifold (1), booster vacuum hose (2), power brake booster (3), master cylinder (4), primary brake tube (5), secondary brake tube (6), ABS ICU (7), master cylinder mounting nuts (8)
  16.  
  17. Remove vacuum seal located on mounting flange of master cylinder. Vacuum seal is removed from master cylinder by carefully pulling it off rear of master cylinder. Do not attempt to pry seal off master cylinder by inserting a sharp tool between seal and master cylinder casting.
  18.  
  19. Disconnect four Chassis brake tubes at ABS ICU. Cap off brake tubes and install sealing plugs in open brake tube outlet ports of ICU.
  20.  
  21. Disconnect 47-way wiring connector at CAB.
  22.  
  23. Loosen 2 bolts fastening ABS ICU bracket to frame rail.

    Click image to see an enlarged view

    Fig. Location of the ICU mounting bolts on the frame rail (1), harness (CAB) wiring connector (2) and location of the CAB mounting to the ICU (3)

    Location of the ICU mounting bolts on the frame rail (1), harness (CAB) wiring connector (2) and location of the CAB mounting to the ICU (3)
  24.  
  25. Lift ICU off frame rail bolts and remove from vehicle.
  26.  
  27. If CAB and HCU need to be separated, perform the following:
    1. Remove 3 screws attaching CAB to HCU.
    2.  
    3. Remove CAB from HCU.
    4.  

  28.  

To install:

  1. Install the CAB to the HCU, if removed.
  2.  
  3. Place ICU with mounting bracket over two mounting bolts in frame rail. Tighten the bolts to 18 ft. lbs. (24 Nm).
  4.  
  5. Connect 47-way wiring connector at CAB.
    NOTE
    When installing chassis brake tubes on ICU, install and tighten two center tube nuts before installing the outer tubes. This action makes it easier to fit a crowfoot wrench and torque wrench in to tighten center brake tube nuts.

  6.  
  7. Connect four chassis brake tubes to outlet ports of ICU. Tighten the brake tube nuts to 120 inch lbs. (14 Nm).
    WARNING
    When installing master cylinder on vehicle, a NEW vacuum seal MUST be installed on master cylinder.

  8.  
  9. Install NEW vacuum seal on rear of master cylinder making sure seal fits squarely in mounting groove.
  10.  
  11. Position master cylinder on studs of power brake booster, aligning booster push rod with master cylinder piston.
  12.  
  13. Install two master cylinder mounting nuts. Tighten both mounting nuts to 18 ft. lbs. (25 Nm).
  14.  
  15. Thread primary and secondary brake tubes into ICU ports as shown. Brake tubes must be held securely when tightened to control orientation of flex section. Tighten tube nuts to 120 inch lbs. (14 Nm).
  16.  
  17. Connect wiring harness connector to brake fluid level switch mounted in brake fluid reservoir.
  18.  
  19. Place coolant recovery bottle in its normal mounted position and install nuts fastening it in place.
  20.  
  21. Connect negative battery cable to battery post.
  22.  
  23. Hook up DRBIII® to initialize CAB.
  24.  
  25. Fill master cylinder with clean, fresh Mopar® Brake Fluid or equivalent, then bleed base brakes and ABS, as outlined in this section.
  26.  
  27. Road test vehicle to ensure proper operation of brakes.
  28.  

Mk25e ABS System

The Hydraulic Control Unit (HCU) is mounted to the Antilock Brake Module (ABM) as part of the Integrated Control Unit (ICU). The HCU controls the flow of brake fluid to the brakes using a series of valves and accumulators. A pump/motor is mounted on the HCU to supply build pressure to the brakes during an ABS stop.

  1. Disconnect and isolate the negative battery cable..
    WARNING
    The vacuum in power brake booster must be pumped down (removed) before removing master cylinder from power brake booster. This is necessary to prevent power brake booster from sucking in any contamination as master cylinder is removed. This can be done simply by pumping brake pedal, with vehicle's engine not running, until a firm feeling brake pedal is achieved.

  2.  
  3. With engine not running, pump brake pedal until a firm pedal is achieved (4-5 strokes).
  4.  
  5. Remove nuts fastening coolant recovery bottle in place and reposition bottle with hoses attached out of way.
    WARNING
    Before removing master cylinder from power brake vacuum booster, master cylinder and vacuum booster must be thoroughly cleaned. This must be done to prevent dirt particles from falling into power brake vacuum booster.

  6.  
  7. Thoroughly clean all surfaces of brake fluid reservoir and master cylinder, paying special attention to area where master cylinder attaches to power brake booster. Use only Mopar® Brake Parts Cleaner or equivalent.
  8.  
  9. Disconnect wiring harness connector from brake fluid level switch in master cylinder brake fluid reservoir.

    Click image to see an enlarged view

    Fig. Exploded view of the master cylinder (1), sensor wiring harness connector (2), booster (3) and mounting nut (4)

    Exploded view of the master cylinder (1), sensor wiring harness connector (2), booster (3) and mounting nut (4)
  10.  
  11. Disconnect primary and secondary brake tubes coming from master cylinder at ABS ICU. Cap off brake tubes and install sealing plugs in open brake tube outlet ports of ICU.
  12.  
  13. Remove two nuts attaching master cylinder to power brake booster.
  14.  
  15. Slide master cylinder straight out of power brake booster and remove.
  16.  
  17. Disconnect four Chassis brake tubes at ABS ICU. Cap off brake tubes and install sealing plugs in open brake tube outlet ports of ICU.
  18.  
  19. Disconnect the 47-way connector from the antilock brake module (ABM) by depressing the tabs on each side of the connector cover, then pulling outward and upward on the lower half of the cover until it locks into position pointing straight outward. The connector can then be pulled straight outward off the ABM.
  20.  
  21. Loosen 2 bolts fastening ABS ICU bracket to frame rail.
  22.  
  23. Lift ICU off frame rail bolts and remove from vehicle.

    Click image to see an enlarged view

    Fig. Loosen 2 bolts fastening ABS ICU bracket to frame rail (1), then lift ICU (2) off frame rail bolts and remove from vehicle

    Loosen 2 bolts fastening ABS ICU bracket to frame rail (1), then lift ICU (2) off frame rail bolts and remove from vehicle
  24.  
  25. If ABM and HCU need to be separated:
    1. If the mounting bracket needs to be removed from the ICU, remove the single mounting bolt, then slide the ICU's mounting pins out of the grommets in the bracket. Remove the mounting pins from the ICU as necessary.
    2.  
    3. If not equipped with traction control, remove the three screws attaching the ABM to the HCU.
    4.  
    5. If equipped with traction control, remove the four screws attaching the ABM to the HCU.
    6.  
    7. Separate the ABM from the HCU.
    8.  

  26.  

To install:

  1. If removed, install the ABM to the HCU.
  2.  
  3. Place ICU with mounting bracket over two mounting bolts in frame rail. Tighten bolts to 18 ft. lbs. (24 Nm).
  4.  
  5. With connector cover completely open, install 47-way wiring connector into socket of the ABM and close cover, locking connector in place.
  6.  
  7. Install four Chassis brake tubes into outlet ports of ICU. Tighten brake tube nuts to 120 inch lbs. (14 Nm).
    WARNING
    The seal on the rear of master cylinder is used to create seal for holding vacuum in power brake vacuum booster. Vacuum seal on master cylinder MUST be replaced whenever master cylinder is removed from power brake vacuum booster.

  8.  
  9. Remove vacuum seal located on mounting flange of master cylinder. Vacuum seal is removed from master cylinder by carefully pulling it off rear of master cylinder. Do not attempt to pry seal off master cylinder by inserting a sharp tool between seal and master cylinder casting.
  10.  
  11. Install NEW vacuum seal on rear of master cylinder making sure seal fits squarely in mounting groove.
  12.  
  13. Position master cylinder on studs of power brake booster, aligning booster push rod with master cylinder piston.
  14.  
  15. Install two master cylinder mounting nuts. Tighten both mounting nuts to 18 ft. lbs. (25 Nm).
  16.  
  17. Thread primary and secondary brake tubes into ICU ports as shown. Brake tubes must be held securely when tightened to control orientation of flex section. Tighten tube nuts to 120 inch lbs. (14 Nm).
  18.  
  19. Connect wiring harness connector to brake fluid level switch mounted in brake fluid reservoir.
  20.  
  21. Place coolant recovery bottle in its normal mounted position and install nuts fastening it in place.
  22.  
  23. Connect negative battery cable to battery post.
  24.  
  25. Hook up scan tool to initialize ABM.
  26.  
  27. Fill master cylinder with clean, fresh Mopar® Brake Fluid or equivalent, then bleed base brakes and ABS.
  28.  
  29. Road test vehicle to ensure proper operation of brakes.
  30.  

 
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