Overview - Brake Booster/Brake Master Cylinder

Fig 1: Exploded View Of Brake Booster/Master Brake Cylinder

Courtesy of AUDI OF AMERICA, LLC

1. Nut
   • 23 Nm
   • Replace after removing.
2. Heat Shield
   • Equipped on some models
3. Master Brake Cylinder
   • Cannot be serviced. If malfunctioning, replace as complete unit.
   • Refer to BRAKE MASTER CYLINDER, REMOVING AND INSTALLING 
4. Brake Line
   • 14 Nm
   • Brake master cylinder/primary piston circuit to hydraulic unit
     WARNING:

     • Do not damage the brake hose and brake line.
     • Do not bend the brake line past the specified form.
     • A damaged brake hose or a damaged or bent brake line must be replaced.
5. Brake Line
   • 14 Nm
   • Brake master cylinder/secondary piston circuit to hydraulic unit
     WARNING:

     • Do not damage the brake hose and brake line.
     • Do not bend the brake line past the specified form.
     • A damaged brake hose or a damaged or bent brake line must be replaced.
6. Bolt
   • 8 Nm
7. Brake Lamp Switch -F- /Brake Pedal Switch -F63-
   • Refer to BRAKE LAMP SWITCH, REMOVING AND INSTALLING
8. Brake Fluid Level Warning Switch -F34-
   • Refer to Brake Fluid Level Warning Switch -F34-, REMOVING AND INSTALLING 
9. Brake Fluid Reservoir
   • Refer to BRAKE FLUID RESERVOIR, REMOVING AND INSTALLING 
10. Locating Pin or Stud Bolt
    • Tighten the stud bolt to 5 Nm
    • Slide through the brake fluid reservoir and the master brake cylinder
    • The locking pin must be pushed into the brake fluid reservoir tab.
11. Cap
12. Vacuum Hose
    • With check valve
13. Seal
    • Replace after removing.
14. Plugs
    • To install, coat with brake fluid
15. Brake Booster
    • Function Test:

      -- With the engine switched off, press the brake pedal firmly several times (to reduce the vacuum in the device).

    • Refer to BRAKE BOOSTER, REMOVING AND INSTALLING 
16. Seal
    • Replace after removing.
17. Nut
    • Replace after removing.
    • Refer to Fig 2
18. Seal
    • Replace after removing.
19. Rubber Buffer

Brake Booster - Tightening Specification and Sequence

Fig 2: Brake Booster - Tightening Sequence

Courtesy of AUDI OF AMERICA, LLC

-- Tighten the bolts to 25 Nm in the sequence -3 and 4-.