Warning: not models equipped with ABS, before disconnecting the hydraulic connections (opening the system) Disconnect the battery and do not connect it until the end of pumping. If this is not done, air can enter the return pump of the system, from where it is very difficult, and in some cases impossible, to expel it.
Note: Please read the warning at the beginning before starting work paragraph 8 about the dangers of brake fluid.
Withdrawal
1. Apply the handbrake, raise the front of the vehicle and install the jack stands. Remove the left wheel.
2. Attach a piece of hose to the left front wheel bleeder by lowering the other end into the can as described in paragraph 2. Open the bleed screw and depress the brake pedal a few cuts to expel as much fluid as possible from the master cylinder. When the flow of liquid dries up, wrap the fitting.
3. Place a rag under the master cylinder to absorb fluid. Disconnect the supply hose from the cylinder and plug the holes so as not to drink the liquid further and so that dirt does not enter the system.
4. Disconnect the wiring from the liquid level sensor in the reserve tank.
5. Wipe the area around the tube connections on the side of the master cylinder and spread out with a rag. Remember the location and connection of the tubes, unscrew the connection nuts and remove the tubes. Plug tubes and openings to keep dirt out. Rinse spilled liquid immediately with cold water.
6. Pull the seal off the motor shield in front of the angry cylinder. Release the wiring harness from its fasteners and lift it up so that the cylinder can be removed.
7. Unscrew the two nuts securing the cylinder to the servo amplifier and remove it from the engine compartment. Remove the o-ring installed at the rear of the cylinder and discard it - a new one is required for installation (pic. 10.7).
Pic. 10.7. Compose the parts of the master cylinder and the servo amplifier: 1. Togh T45 bolt; 2. Self-locking nut; 3. Master cylinder; 4. Brake tube; 5. Brake tube; 6. Seal; 7. Amplifier; 8. Gasket; 9. Vacuum hose; 10. Reserve tank; 11. Lid; 12. Seals; 13. Supply hose; 14. Motor shield
Note: If only the master cylinder is being removed, the Tox head bolts are not to be disturbed - they also attach the servo amplifier.
Repair
8. The defective cylinder must be replaced. Audi / VAG repair kits are not available for spare parts - the cylinder is replaced entirely.
9. The only spare parts are the rubber seals in the reservoir. If the seals are damaged, remove the reservoir from them and remove the seals. Lubricate the new seals with clean brake fluid and insert them into the cylinder as follows. so that the seals protrude from the housing by approximately 1 mm.
Installation
10. Make sure the mating surfaces are clean and install a new O-ring on the rear end of the master cylinder.
11. Install the cylinder on the booster studs as follows. so that the pusher of the amplifier enters the piston of the cylinder in the middle. Have an assistant depress the brake pedal lightly to move the rod in the direction of the cylinder.
12. Screw on the fastening nuts, tightening them to the prescribed torque.
13. Wipe the connections and attach the brake pipes, tighten the connection nuts to the prescribed torque.
14. Connect the clutch master cylinder hose to the reserve tank and securely tighten the clamp.
15. Connect the wiring connector to the liquid level sensor.
16. Secure the wiring and re-seal the engine shield.
17. Fill the reserve tank with fresh brake fluid and bleed the hydraulic systems as described in paragraph 2 and chapter 6.
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