E-Series Vans (1997-2005)

Rear Wheel Anti-Lock Brake System (RABS)


Bleeding The RWAL System

The RABS system is bleed in the same manner as a conventional brake system. Refer to brake bleeding in this section.

General Information

The Rear Wheel Anti-lock Brake System (RABS) is an electronically operated, hydraulically controlled rear wheel brake control system. Major components include the vacuum power brake booster, master cylinder, the speed sensor, and the control valve or Hydraulic Control Unit (HCU) and the control module.

The system is designed to retard rear wheel lockup during periods of high wheel slip when braking. Retarding the rear wheel lockup is accomplished by modulating fluid pressure to the rear wheel brake circuit. When the control module detects a variation in voltage across the speed sensor, the RABS is activated. The control module opens and closes various valves located inside the HCU/control unit. These valves, called dump and isolation valves, modulate the hydraulic pressure to the rear wheels by applying and venting the pressure to the brake fluid circuits.

Removal & Installation

Tone (Exciter) Ring

The exciter ring is located in the differential case inside the axle housing on the rear gear. The rear differential must be disassembled to replace the ring. Refer to Section 7.

Speed Sensor

Removal & Installation

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Fig. Detach the connector on the speed sensor

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Fig. Remove the sensor hold-down bolt and ...

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Fig. Remove the sensor

The sensor is located on the rear axle housing.

  1. Raise and safely support the vehicle securely on jackstands.
  3. Carefully clean the axle surface to keep dirt from entering the housing.
  5. Detach the connector on the speed sensor.
  7. Remove the sensor hold-down bolt.
  9. Remove the sensor.
  11. If a new sensor is being installed, lubricate the O-ring with clean engine oil. Carefully push the sensor into the housing aligning the mounting flange hole with the threaded hole in the housing. Tighten the hold-down bolt to 30 ft. lbs. (41 Nm)-If the old sensor is being installed, clean it thoroughly and install a new O-ring coated with clean engine oil.
  13. Attach the connector on the speed sensor.
  15. Lower the vehicle.