Genuine Audi 100 Brake Master Cylinder

Audi 100 Brake Master Cylinder Parts and Q&A

• Master Cylinder
  4A0-611-021-D
  Q: What precautions should be taken regarding the Brake Master Cylinder before starting work to address the dangers of hydraulic fluid on Audi 100?

  A:

  Prior to going to work, remember to deal with the risks of hydraulic fluid. Wipe off the master cylinder fluid reservoir and take off the cap. Place a container below the outlet of the clutch master cylinder fluid, loosen the retaining clip and detach the hose of the clutch master cylinder as well as the ABS hydraulic unit hose (where applicable). It is recommended that the reservoir should be emptied into the container with the hose ends plugged to ensure that the fluids are not wasted and dirt is not introduced into the set up. Unfitting of the wiring plug to the level sender unit of brake fluid, clean up around the unions of brake pipe on the master cylinder, and place absorbent rags under to absorb any excess fluid. Record the proper locations of the unions, unscrew them, and stuff in the ends and holes of the pipes to reduce the loss of brake fluid and dirt intrusion, and wash the spilled fluid with cold water. Disassemble the two nuts holding the master cylinder onto the vacuum servo unit and pull the unit out of the engine compartment removing the sealing ring and preparing to install a new one when reassembling. In case the master cylinder is defective, it should be removed and replaced with another one, the mounting seals of the fluid reservoir can be replaced in case they are worn out, but repair kits are not provided. Apply clean brake fluid to new seals and be sure that they are properly fitted, especially the rear seal, which must protrude some 1 mm of its housing. Once the seals are fitted in place, place the fluid reservoir in place. Wipe off the mating surfaces of the master cylinder and servo unit, replace the sealing ring, and connect the master cylinder to the servo unit making sure that the parts are aligned. Install the mounting nuts again, clean the brake pipe unions, and rejoin them to the master cylinder ports and tighten them to the required torque. Re-attach the hoses to the reservoir and ensure that the retaining clips are tightened, re-attach the wiring of the fluid level sender unit, refill the master cylinder reservoir with new fluid and bleed off the entire hydraulic system.