ABS System Components — Removal and Installation (Audi A4 B5)

Hydraulic block

Warning: On ABS models, disconnect the battery before opening the hydraulic system and do not reconnect the battery until the system has been bled. Failure to do so may cause air to enter the hydraulic pump, where it will be extremely difficult to remove, requiring specialized diagnostic equipment (see paragraph 2).

Note: Audi states that after removal and installation of the units, the system operation must be checked using specialized equipment. Taking this into account, it is recommended to entrust the removal and installation of the units to specialists of the dealer car service. If you decide to carry out these operations yourself, check the system on diagnostic equipment at the earliest opportunity.

Removal

1. Disconnect the negative cable from the battery.

2. If necessary, unscrew the fastening screw and remove the plastic relay cover from the hydraulic unit of the regulator.

3. Release the latch and disconnect the wiring connector from the hydraulic unit.

4. If necessary, unscrew the nut and disconnect the ground wire from the regulator.

5. Raise the front of the vehicle and install safety stands. Remove the left front wheel.

6. Attach a section of hose to the left caliper fitting, lowering the other end into the jar, as described in paragraph 2. Open the nipple and press the brake pedal all the way down and secure it there with a wooden block, resting it against the seat. After finishing removing the fluid, tighten the nipple.

Note: The brake pedal must be kept depressed until the hydraulic pipes are fully connected to the hydraulic unit, until the very end of the procedure.

7. Wipe the area around the tube connections. Remember how the tubes are connected to the unit so that they can be installed correctly during assembly. Unscrew the connection nuts and carefully remove the tubes. Isolate the tubes from dirt getting into the system. Immediately wash away any spilled liquid.

8. Loosen the hydraulic unit mounting nuts and remove the unit from the engine compartment. If necessary, the mounting bracket can be removed by unscrewing the mounting bolts. Damaged or worn regulator supports must be replaced.

Note: When removing and storing, keep the unit upright to prevent liquid from spilling out and air from entering.

Installation

Note: New units are supplied as spare parts fully bled and filled with brake fluid. It is vital to keep the plugs closed until the tubes are connected to prevent air from getting inside.

9. Install the block on the bracket and tighten the mounting nuts to the specified torque.

10. Remove the plugs and connect the hydraulic pipes to their places. Tighten the union nuts to the specified torque.

11. Connect the wiring connector to the hydraulic unit and, if equipped, install the cover.

12. Fill the reserve tank with fresh brake fluid (see Weekly Checks) and connect the battery.

13. Remove the brake pedal stop and bleed the entire hydraulic system as described in paragraph 2. Check the brakes before driving on the road. Contact your dealer to have the ABS system checked as soon as possible.

Electronic control unit Bosch ABS 5.0

Removal

14. Remove the rear seat cushion as described in chapter 11 to gain access to the BEU.

15. Loosen the mounting screws and remove the unit.

16. Turn off the ignition, release the latch and disconnect the wiring connector from the unit. Remove the unit from the car.

Installation

17. Installation - reverse procedure.

Front wheel sensor

Removal

18. Disconnect the ground wire from the battery.

19. Apply the handbrake. Place chocks under the rear wheels. Raise the front of the car and install safety stands. Remove the wheel in question.

20. Follow the wiring from the sensor, free it from all fasteners and remember the layout. Disconnect the wiring connector.

21. Carefully pull the sensor out of the steering knuckle bracket and remove it from the vehicle. Once the sensor is removed, remove the rubber seal and retaining sleeve from the bracket (fig. 19.21).

Installation

22. Make sure the sensor and its mounting surface in the steering knuckle are clean and apply a small amount of fine copper based grease.

23. Insert the bushing into the rack until it stops, then insert the sensor with the rubber seal. Correctly lay and secure the wiring and push the sensor until it stops.



24. Connect the wiring connector.

25. Install the wheel (if you filmed) and lower the vehicle. Tighten the wheel bolts to the specified torque as described in Chapter 1A or 1B. Connect the battery.

Rear wheel sensor

Removal

26. Disconnect the ground wire from the battery.

27. Remove the rear seat cushion as described in chapter 11 and locate the sensor wiring connector. Disconnect the connector and release the wiring from the fasteners.

28. Place chocks under the front wheels, engage reverse (or "P" in the case of an automatic transmission) gear. Raise the rear of the car and install safety supports. Remove the corresponding wheel.

29. Follow the wiring from the sensor to the connector and release the sensor wiring from the common braid. Unscrew the mounting bolts and remove the protective cover of the wiring from the rear beam, release the rubber seal in the body opening and pull the wiring so that it can be removed together with the sensor.

30. Carefully pull the sensor out of the rear beam and remove it from the car. After removing the sensor, remove the bushing (fig. 19.30, a, b).

Installation

31. Make sure the mating surfaces of the lever and sensor are clean. Lubricate the locking sleeve and sensor with fine copper grease.



32. Insert the bushing into the hole in the rear beam, then insert the sensor. Put the sensor wiring in place and insert the sensor until it stops.

33. Make sure the wiring is routed correctly and secure it with all fasteners. Install the protective cover on the rear beam, tightening the fastening screws securely. Push the wiring into the body opening and install the rubber seal.

34. Install the rear wheel, lower the vehicle. Tighten the wheel mounting bolts to the specified torque as described in Chapter 1A or 1B.

35. Connect the sensor wiring connector, install the rear seat cushion and connect the battery.

[The original article is available on the website AUDIMANUAL.ru]