Brake Booster And Brake Master Cylinder Assembly Overview

Fig 1: Brake Booster/Brake Master Cylinder Assembly Overview

Courtesy of AUDI OF AMERICA, LLC

1. Gasket
   • For brake booster.
2. Brake Booster
   • On certain vehicles, the necessary pressure is removed at the intake manifold.
   • Vehicles with OHBV have a Brake Booster Vacuum Sensor G483 installed. Refer to BRAKE BOOSTER VACUUM SENSOR, WITH OPTIMIZED HYDRAULIC BRAKE VACUUM (OHBV) BOOSTING .

     Functional Check

     • With engine switched off, depress brake pedal firmly several times (to deplete vacuum in tool).
     • Press and hold brake pedal.
     • Start engine.
     • If brake booster is functioning correctly, brake pedal slackens noticeably under foot.
   • Disconnect from brake pedal. Refer to BRAKE PEDAL AND BRAKE BOOSTER, SEPARATING .
   • Removing and installing, refer to BRAKE BOOSTER .
   • Removing and installing, TT RS, refer to BRAKE BOOSTER, TT RS 
     NOTE:

     If the vehicle has a TFSI engine, then the noise amplifier must be removed and installed. Refer to NOISE AMPLIFIER, TFSI .

     If the vehicle has a TTS engine, then the noise amplifier must be removed and installed. Refer to NOISE AMPLIFIER, TFSI .

     The noise amplifier is inside the engine compartment in front of the brake booster.

   • Replace as complete unit if malfunctioning.
3. Seal
   • Replace
4. Brake Master Cylinder
   • With attached brake light switch ABS/ESP MARK 60 BRAKE SYSTEM COMPONENT AND INSTALLATION LOCATION OVERVIEW => List Item:13 - .
   • Cannot be serviced.
   • Replace as complete unit if malfunctioning.
   • Removing and installing, refer to BRAKE MASTER CYLINDER .
   • Removing and installing, TT RS, refer to BRAKE MASTER CYLINDER, TT RS 
     NOTE:

     • If the vehicle has a TFSI engine, then the noise amplifier must be removed and installed. Refer to NOISE AMPLIFIER, TFSI .
     • If the vehicle has a TTS engine, then the noise amplifier must be removed and installed. Refer to NOISE AMPLIFIER, TFSI .
     • The noise amplifier is inside the engine compartment in front of the brake booster.
5. Heat Shield
6. Nut
   • Self-locking.
   • Always replace after removal.
   • 20 Nm
7. Brake Line
   • Brake master cylinder/secondary piston circuit to hydraulic unit.
   • 14 Nm
8. Brake Line
   • Brake master cylinder/primary piston circuit to hydraulic control unit.
   • 14 Nm
9. Sealing Plugs
   • Coat with brake fluid and insert into brake master cylinder.
10. Brake Fluid Reservoir
    • Coat with brake fluid and insert into sealing plugs in brake master cylinder.
    • With floating insert with integrated brake fluid level warning switch.
    • To replace the warning switch, remove brake fluid reservoir.
    • Press brake fluid reservoir into sealing plugs.
    • Removing and installing, refer to BRAKE FLUID RESERVOIR .
11. Cap
    • With integrated floater and brake fluid level warning switch.
12. Vacuum Tube
    • With check valve.
13. Sealing Plugs

Fig 2: Checking Inner Boot Of Brake Booster

Courtesy of AUDI OF AMERICA, LLC

-- Remove driver side compartment. Refer to Removal and Installation .

-- Make sure that boot did not slip out of the circumferential groove, as shown here.