Alero, Grand Am 1999-2005

Hydraulic Modulator/Master Cylinder Assembly

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The hydraulic modulator is mounted to the side of the master cylinder. The master cylinder must be removed from the vehicle to allow the modulator to be separated.

Removal & Installation




CAUTION
A Tech I® scan tool (or equivalent) is required to relieve the gear tension in the hydraulic modulator. This procedure must be performed prior to removal of the brake control and motor assembly. Attempting to remove the master cylinder without relieving the gear tension can cause personal injury.

  1. Remove the master cylinder from the vehicle, as detailed earlier in this section.
  2.  
  3. Remove the Torx® head screws that attach the gear cover to the bottom of the modulator, and remove the gear cover.
  4.  
  5. Remove the 4 Torx® head screws that connect the motor pack to the to the modulator assembly.
  6.  
  7. Carefully remove the motor pack from the modulator assembly.
  8.  
  9. Remove the two brake modulator-to-master cylinder bolts, and carefully separate the modulator from the master cylinder.
  10.  
  11. Remove the two transfer tube from the brake modulator or master cylinder.
  12.  
  13. Remove any banjo bolt O-rings that are stuck to the modulator or master cylinder.

    Click image to see an enlarged view

    Fig. Exploded view of the ABS Hydraulic Modulator assembly mounting (motor pack removed)

  14.  

To install:

  1. Install the new transfer tubes as follows:
    1. Install new O-rings on both sides of each new transfer tube.
    2.  
    3. Using fresh, clean brake fluid, (of the proper type) lubricate the new O-rings on both sides of each transfer tube.
    4.  
    5. Install the transfer tube assemblies into the ports on the brake modulator. Push them in by hand, until they bottom out in the port.
    6.  

  2.  
  3. Using new O-rings, lubricated with clean brake fluid, install them onto the master cylinder and brake modulator.
  4.  
  5. With the mounting flange of the master cylinder in a vise, carefully align the transfer tubes with the ports in the master cylinder, and rock the modulator into position.
  6.  
  7. Make sure the transfer tubes are positioned properly, and install and tighten the two modulator-to-master cylinder bolts to 18 ft. lbs. (24 Nm).
  8.  
  9. With the master cylinder/modulator assembly upside down, (looking down at the gears) rotate each modulator gear counterclockwise until it stops.
  10.  
  11. Install the motor pack onto the modulator/master cylinder assembly. Tighten the four Torx® screws to 44 in. lbs. (5 Nm).
  12.  
  13. Install the gear cover onto the modulator/master cylinder assembly. Tighten the Torx® screws to 36 in. lbs. (4 Nm).
  14.  
  15. Install the master cylinder/modulator assembly to the vehicle as detailed earlier in this section.
  16.  
  17. Bleed the master cylinder/modulator assembly of air as described in this section.
  18.  

 
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