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    1985 Volvo 244DL 2.3L FI 4cyl

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    Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

    Hydraulic Actuator

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    DESCRIPTION



    The actuator is located in the engine compartment. The actuator contains the solenoid control valves, pump(s) to return fluid to the brake master cylinder, reservoirs for temporary collection of brake fluid released from the lines as well as check and relief valves.

    The relays and solenoids are controlled by the ECU. Under normal braking conditions, the solenoids are in the open or pressure-build position, allowing brake fluid to pass proportional to pedal pressure. During anti-lock function, the solenoids are commanded into positions to either hold or release brake fluid line pressures as required. When anti-lock function is no longer needed, the solenoids reset to the normal position. Additionally, if the ECU detects a system fault, the solenoids are immediately released to the normal or default position.

    The control relays for the pump motor and solenoid valves are located externally on/or near the actuator. The relays are controlled by the ECU and are the only actuator components that can be serviced separately. Any other failure associated with the actuator requires the entire unit to be replaced.

    REMOVAL & INSTALLATION



    See Figures 1 and 2



    Click image to see an enlarged view

    Fig. Fig. 1: ABS actuator assembly-1991-94 vehicles



    Click image to see an enlarged view

    Fig. Fig. 2: ABS actuator assembly-1995-96 vehicles

    1. Disconnect the negative battery cable.
    2.  
    3. Drain the brake fluid from the system. Use a syringe or similar tool to drain the fluid reservoir.
    4.  
    5. Drain the power steering fluid.
    6.  
    7. Properly discharge the air conditioning system using correct refrigerant recovery equipment.
    8.  
    9. Disconnect the power steering line and hose.
    10.  
    11. Disconnect all connectors from the actuator relay bracket.
    12.  
    13. Remove the mounting nut for the relay bracket.
    14.  
    15. Remove the bolt holding the relay bracket. The bolt is located just below the relays.
    16.  
    17. Remove the actuator relay box with its bracket.
    18.  
    19. At the top of the actuator, disconnect the 2 brake lines running from the actuator to the master cylinder. It is not necessary to disconnect the lines at the master cylinder.
    20.  
    21. Completely remove the 2 lines running from the actuator to the dual proportioning valve.
    22.  
    23. Remove or loosen the mounting nuts holding the actuator to the bracket.
    24.  
    25. Remove the actuator grounding bolt.
    26.  
    27. Carefully lift the actuator forward and out of the vehicle.
    28.  

    To install:
    1. Install the actuator into the vehicle.
    2.  
    3. Install the grounding bolt.
    4.  
    5. Install and tighten the nuts holding the actuator to its bracket.
    6.  
    7. Connect the brake lines between the actuator and the proportioning valve. Tighten the fittings to 13 ft. lbs. (17 Nm).
    8.  
    9. Connect the 2 brake lines to the top of the actuator, tightening them to 13 ft. lbs. (17 Nm).
    10.  
    11. Install the air conditioning lines.
    12.  
    13. Install the relay bracket, then install the relay box.
    14.  
    15. Connect the harness connectors to their mounts on the relay bracket.
    16.  
    17. Install the power steering line and hose.
    18.  
    19. Refill the power steering fluid.
    20.  
    21. Refill the brake fluid and bleed the system thoroughly.
    22.  
    23. Connect the negative battery cable.
    24.  
    25. Recharge the air conditioning system.
    26.  

     
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