Hydraulic modulator
Attention! On models equipped with ABS, be sure to disconnect the battery before disconnecting the hydraulic brake lines. Connect the battery only after connecting all the hydraulic lines of the brake path. Violation of this requirement is fraught with air entering the hydraulic modulator, the removal of which during the normal bleeding of the system (see the text of Section) is not possible and requires the use of a special electronic tester (VAG 1552).
Before starting work, read the warning text at the beginning of the Section System design, description of individual components and mechanisms.
Removing
Note. Prepare plugs for sealing open fittings. When assembling, you will also need new mounting nuts.
1. Disconnect the negative cable from the battery. In order to minimize the loss of hydraulic fluid, remove the cap in the GTZ reservoir, place a polyethylene plug under it and screw it tightly into place.
2. Release the lock and disconnect the electrical connector on the hydraulic modulator block.
3. Thoroughly wipe the surfaces of the GTZ and the modulator around the fittings for connecting the brake lines. Mark the pipes to be disconnected.
4. Give cap nuts of union connections of the hydraulic lines connecting ГТЦ with the modulator. Separate the lines from the receiving fittings and remove them from the vehicle. Seal the open ends of the fittings immediately.
Note. The nuts can be tightened quite tightly, and therefore, in order to avoid rounding of the slots, they should be unscrewed using a special ring wrench with a split head. Prepare to collect spilled liquid.
5. Give nipple nuts and disconnect the remaining four brake tubes from the hydraulic modulator. Seal the open ends of the fittings.
6. Give nuts of fastening of an arm of the modulator to the block of the servo drive of the vacuum booster of brakes. While supporting the GTZ, remove the modulator from its place.
Installation
Installation is in the reverse order. Pay special attention to the following points:
- a) Do not forget to replace the fixing nuts and make sure that they are tightened with the required force;
- b) Before connecting the brake lines, fill them with (and fittings on the modulator) fresh hydraulic fluid (see Section Bleeding the hydraulic system). Follow the correct connection of the tubes and the reliability of tightening the union nuts;
- c) Track reliability of fixing of an electric socket by a clip;
- d) Bleed the hydraulic system (see Section Bleeding the hydraulic system) and connect the negative wire to the battery;
- e) At the earliest opportunity, drive the car to a workshop to check the correct functioning of the ABS using special diagnostic equipment.
Electronic control unit (ECU)
Removing
Note. Prepare plugs to seal open union connections after removing the ECU separation from the hydraulic modulator.
1. Remove the hydraulic modulator assembly from the ECU.
2. Remove the bolts securing the ECU to the base of the hydraulic modulator. Release the clips and separate the ECU from the modulator. Seal the open ends of the fittings on the modulator immediately with pre-prepared plugs.
Attention! Do not tilt or turn the ECU removed from the modulator to avoid damaging the valve pins.
Installation
Installation is in the reverse order.
Note. Use extreme caution when mating the ECU to the modulator. Tighten the mounting bolts diagonally to the required torque and install the hydraulic modulator in its original place on the vehicle.
Front wheel sensors
Removing
1. Disconnect the negative cable from the battery.
2. Apply the parking brake, then jack up the front of the vehicle and place it on jack stands. Remove the corresponding front wheel.
3. Walk from the sensor along the electrical wiring, releasing it from the intermediate clamps and remembering the laying route. Disconnect the electrical connector.
4. Remove the fixing bolt and remove the sensor from the hub assembly.
Installation
1. Thoroughly clean the mating surfaces of the transducer and hub assembly, then lightly lubricate the walls of the transducer seat in the hub with a multipurpose grease such as Gleitmo 165 or Wolfracote.
2. Check the condition of the working element of the sensor, then put the latter in its regular place in the hub assembly. Screw in the mounting bolt and tighten it to the required torque.
3. Moving along the electrical wiring, fix it in all provided intermediate clamps. Connect the electrical connector. Reinstall the wheel, lower the vehicle to the ground and tighten the wheel bolts to the correct torque.
Rear wheel sensors
Removing
1. Chock the front wheels, then jack up the rear of the vehicle and place it on jack stands. Remove the corresponding rear wheel.
2. Walk from the sensor along the electrical wiring, releasing it from the intermediate clamps and remembering the laying route. Disconnect the electrical connector.
3. Turn out a fixing bolt and remove the gauge from a nave of the bridge.
Installation
1. Thoroughly clean the mating surfaces of the transducer and hub assembly, then lightly lubricate the walls of the transducer seat in the hub with a multipurpose grease such as Gleitmo 165 or Wolfracote.
2. Check the condition of the working element of the sensor, then put the latter in its regular place in the hub assembly. Screw in the mounting bolt and tighten it to the required torque.
3. Moving along the electrical wiring, fix it in all provided intermediate clamps. Connect the electrical connector. Reinstall the wheel, lower the vehicle to the ground and tighten the wheel bolts to the correct torque.