Overview - Brake Booster/Brake Master Cylinder

Fig 1: Exploded View Of Brake Booster/Brake Master Cylinder (Electromechanical Brake Booster)

Courtesy of AUDI OF AMERICA, LLC

1. Brake Line
   • Brake master cylinder/primary piston circuit to hydraulic unit
   • Tightening Specifications
     • With standard tool: 14 Nm
     • With special tool Refer to Fig 3 12 Nm
2. Brake Master Cylinder
   • There are different versions. Refer to the Electronic Parts Information for the allocation.
   • Cannot be serviced. If malfunctioning, replace as complete unit.
   • Refer to BRAKE MASTER CYLINDER, REMOVING AND INSTALLING 
3. Brake Line
   • Brake master cylinder/secondary piston circuit to hydraulic unit
   • Tightening Specifications
     • With standard tool: 14 Nm
     • With special tool Refer to Fig 3 12 Nm
4. Plugs
   • Replace the brake master cylinder if damaged
   • To install, coat with brake fluid
5. Brake Fluid Reservoir
   • There are different versions. Refer to the Electronic Parts Information for the allocation.
   • Refer to BRAKE FLUID RESERVOIR, REMOVING AND INSTALLING 
6. Locking Pin
   • Slide through the brake fluid reservoir and the master brake cylinder
   • The locking pin must be pushed into the brake fluid reservoir tab.
7. Brake Fluid Level Warning Switch -F34-
   • Refer to Brake Fluid Level Warning Switch -F34-, REMOVING AND INSTALLING 
8. Cap
   • With gasket
   • The seal is not available separately
9. Nut
   • Self-locking
   • Replace after removing
   • Refer to Fig 2
10. Seal
    • Replace after removing
11. Brake Booster -NX6-
    • with
      • Brake Pedal Position Sensor -G100-
      • Brake Pedal Position Sensor 2 -G836-
      • Power Supply Sensor 1 -G730-
      • Power Supply Sensor 2 -G731-
      • Brake Booster Voltage Sensor -G822-
      • Brake Booster Temperature Sensor 1 -G838-
      • Brake Booster Temperature Sensor 2 -G839-
      • Brake Booster Motor Position Sensor -G840-
      • Brake Booster Control Module -J539-
      • Electro-Mechanical Brake Booster Motor -V548-

      The components in the brake booster cannot be replaced individually.

      Check the function of the brake lamp after installation of the brake booster.

    • Refer to BRAKE BOOSTER, REMOVING AND INSTALLING 
12. O-Ring
    • Replace the brake master cylinder if damaged
13. Nut
    • 23 Nm

Brake booster - tightening specification and sequence

Fig 2: Brake Booster - Tightening Sequence

Courtesy of AUDI OF AMERICA, LLC

-- Tighten the nuts to 25 Nm in the sequence -3 and 4- (shown on LHD).

Brake lines tightening using special tools

Fig 3: Special Tool Assembly For Tightening Brake Lines

Courtesy of AUDI OF AMERICA, LLC

Special tools and workshop equipment required 

• Open Ring Spanner Insert - AF 11mm:V.A.G 1410/6 
• Torque Wrench - Universal Joint :V.A.G 1410/7 
• Mini Torque Wrench:VAS 6854 

Heat shield - tightening specification

Fig 4: Heat shield - tightening specification

Courtesy of AUDI OF AMERICA, LLC

-- Tighten the bolt -arrow- to 8 Nm.