Models with Automatic Speed Regulator (ASR) (Mercedes-Benz E-Class W124)

Removal

1. Remove the ground cable from the battery.

2. Unscrew the screws and remove the cover from the hydraulic device.

3. Place a clean transparent hose on the bleed nipple of the hydraulic device (marked SP) and install the other end of the hose in a container. Unscrew the bleed nipple and drain the brake fluid into the container.

4. Release the mounting bracket and disconnect the electrical connector from the hydraulic unit.

5. Disconnect the brake pipes from the hydraulic unit.

6. Unscrew the nut and remove the ground bus from the hydraulic block.

7. Unscrew the bolts and remove the hydraulic device.

Attention! Do not disassemble the hydraulic device modulator, as it is not intended for repair.

Installation

1. Installation is carried out in the reverse order of removal, taking into account the following points:

• a - check the condition of the rubber bushings and replace them if necessary;
• b - in accordance with the previously made markings, connect the brake pipes to the hydraulic device and secure them with nuts, tightening them to the required torque;
• c - remove air from the brake system.

ASR system pump

Removal

1. Remove the ground cable from the battery.

2. Unscrew the screws and remove the cover from the hydraulic device.



3. Place a clean transparent hose on the bleed nipple of the hydraulic device (marked SP) and install the other end of the hose in a container. Unscrew the bleed nipple and drain the brake fluid into the container.

4. To reduce brake fluid loss, pinch the hose connecting the pump to the master cylinder reservoir.

5. Wipe the area around the pump hose connection and the tube connections. Unscrew the union nuts and carefully remove the tubes from the pump. Also disconnect the hose from the pump. Close the ends of the tubes and hose with plugs.

6. Disconnect the electrical connector from the pump, then remove the pump from the bracket and remove it from the engine compartment.

Installation

1. Installation is carried out in the reverse order of removal, taking into account the following points:

• a - check the condition of the rubber seal of the pump and replace it if necessary;
• b - remove air from the brake system and also from the hydraulic device.

Pressure accumulator

Removal

1. Remove the ground cable from the battery.

2. Unscrew the screws and remove the cover from the hydraulic device.

3. Place a clean transparent hose on the bleed nipple of the hydraulic device (marked SP) and install the other end of the hose in a container. Unscrew the bleed nipple and drain the brake fluid into the container.

4. Disconnect the pressure accumulator tubes from the base of the hydraulic unit.

5. Apply the parking brake, then raise the front of the vehicle and secure it on stands. Remove the left front wheel.



6. Unscrew the screws and remove the wing guard from under the left wing arch.

7. Unscrew the nuts securing the pressure accumulator to the bracket, then carefully remove the pressure accumulator together with the tubes.

Installation

1. Installation is carried out in the reverse order of removal, taking into account the following points:

• a - when installing, check that the tubes are connected correctly to the hydraulic device;
• b - tighten the connecting nuts of the tubes to the required torque;
• c - remove air from the brake system and hydraulic device.

Electronic Control Unit (ECU)

Removal

1. The ABS electronic control unit is located under a plastic cover and mounted on the rear of the battery tray. Remove the ground cable from the battery.

2. Remove the rubber seal and cover. To improve access to the electronic control unit, remove the rubber seal located at the base of the windshield, then detach the mounting bracket, unscrew the screws and remove the side section of the ventilation shroud.

3. Release the retaining clips and disconnect the electrical connectors from the ECUs, then remove the ECU from the socket. The hydraulic ECU is installed behind the throttle position actuator ECU.

Installation

1. Installation is carried out in the reverse order of removal.

Front wheel sensor

Removal

1. Apply the parking brake, then raise the front of the vehicle and secure it on stands. Remove the affected front wheel.

2. Make sure the ignition is off, then remove the electrical connector from the mounting bracket and disconnect it from the main wiring harness. Remove the sensor wiring from the mounting brackets and retainers.



3. Unscrew the bolt securing the sensor to the steering knuckle and remove the sensor together with the wires. Check the condition of the sensor sealing ring and replace it if necessary. When installing the sensor, use a new mounting bolt.

Installation

1. Clean the wheel sensor and the wheel sensor rotor grooves from dirt. Apply a thin layer of grease to the mating surfaces of the sensor and the steering knuckle.

2. Install the sensor sealing ring.

3. Install the wheel sensor into the steering knuckle and secure with new bolts, tightening them to the specified torque.

4. Secure the sensor wiring with clamps and fasteners. Check that the electrical connector sealing ring is in good condition, then connect the electrical connector and secure it with a clamp.

5. Install the wheel, then lower the vehicle to the ground and tighten the wheel bolts to the specified torque.

Rear wheel sensor

Caution: When installing the rear wheel sensor, you must use a new sensor mounting bolt and a new rear final drive mechanism nut, as well as a new sensor sealing ring.

Removal

1. Raise the rear of the vehicle and support it on stands.

2. Unscrew the nuts and remove the casing securing the sensor wiring to the underbody of the vehicle.

3. Place a jack with a wooden block under the rear final drive housing and raise the jack enough so that the weight of the rear final drive is supported by the jack.

4. Remove the two nuts and bolts securing the rear of the final drive.

5. Unscrew the nut and remove the bolt securing the front part of the final drive.



6. Carefully lower the rear final drive until the driveshaft just touches the crossmember. Mark the location and remove the washers and rubber pads from the rear final drive front mount. Check the condition of the rubber pads and replace if necessary.

7. Unscrew the bolt and remove the sensor together with the sealing ring from the rear final drive housing. Replace the sensor sealing ring.

8. Locate the sensor electrical connector and remove the electrical connector cover. Turn the locking ring and disconnect the electrical connector.

9. If it is necessary to remove both sensors at the same time, label the wires and electrical connectors of the sensors.

Installation

1. In accordance with the previously made markings, connect the electrical connectors of the sensor and install the cover.

2. Clean the mating surfaces of the sensor and the rear final drive housing and install new sensor seals.

3. Install the sensors on the rear final drive housing and secure with bolts, tightening them to the required torque.

4. Check that the rubber pads and washers are correctly installed on the front of the rear final drive and return the rear final drive to its original position.

5. Secure the rear final drive with bolts, screwing new nuts onto them and tightening them to the required torque.

6. Check that the sensor wiring is correctly positioned, then install the wiring cover and lower the vehicle.

Front wheel sensor toothed rotor

The front wheel sensor toothed rotor is mounted on the rear of the wheel hub. Clean the grooves and check the condition of the rotor teeth. If the rotor needs to be replaced, the hub assembly must be replaced.

Rear wheel sensor toothed rotors

The toothed rotors of the rear wheel sensors are an integral part of the rear main gear. Remove the rear wheel sensors and check the condition of the rotor teeth through the sensor holes. To replace the toothed rotor of the rear wheel sensor, the rear main gear must be disassembled and this work must be performed at a service station.

Protection relay

Removal

1. The protection relay is located near the electronic control unit (ECU). Before removing the relay, make sure the ignition is off.

2. Unscrew the mounting screw, pull the relay out of the socket and remove it from the engine compartment.

Installation

1. Check the condition of the protection relay connecting contacts on the relay and in the relay installation socket.

2. Installation is carried out in the reverse order of removal.

ASR relay

Removal

1. Unscrew the screw and remove the relay cover from the hydraulic device.

2. Make sure the ignition is off and remove the required relay from the control unit. The solenoid valve relay is smaller in size than the return pump relay.

Article was borrowed from the website [MERCEDESMAN.ru]