Brake Booster/Brake Master Cylinder Overview

Brake Booster/Brake Master Cylinder Overview

• Use only new brake fluid. Observe information on brake fluid reservoir!

I - All vehicles.

II - Brake vacuum pump (V192) for hybrid vehicles. Assembly overview, refer to => [ Brake System Vacuum Pump Overview ] Brake System Vacuum Pump Overview.






1 Brake Pedal

• Removing and installing, refer to => [ Brake Pedal ] Brake Pedal.

• Separate the brake pedal from brake booster. Refer to => [ Brake Pedal and Brake Booster, Separating and Connecting ] Brake Pedal and Brake Booster, Separating and Connecting.

• Clip brake pedal together with brake booster. Refer to => [ Brake Pedal and Brake Booster, Separating and Connecting ] Brake Pedal and Brake Booster, Separating and Connecting.

• Allocation, refer to the Electronic Parts Catalog (ETKA).

2 Mounting Bracket for Pedal Assembly

3 Nut

• Self-locking

• 23 Nm

• Always replace if removed.

4 Gasket

• For brake booster.

5 Brake Booster

• On gasoline engines, vacuum is supplied from intake manifold.

• Hybrid vehicles with a gasoline engine have an electric brake vacuum pump.

• On diesel engines, a vacuum pump is installed for vacuum creation.

• Functional check:

- With engine switched off, depress brake pedal firmly several times (to exhaust the vacuum in the unit).

- Depress and hold brake pedal with average foot pressure and start engine. If brake booster is working properly, pedal will be felt to give noticeably under foot (booster assistance becomes effective).

• Replace completely if there are malfunctions (check the vacuum system for the brake booster first; refer to => [ Brake Booster Vacuum System, Checking ] Testing and Inspection).

• Removing and installing, refer to => [ Brake Booster ] Brake Booster.

6 Seal

7 Bolt

• 5 Nm

8 Clip

9 Brake Lamp Switch (F)

• Removing and installing, refer to => [ Brake Lamp Switch (F) ] Service and Repair.

10 Nut

• Self-locking

• 23 Nm

• Always replace if removed.

11 Brake Master Cylinder

• Cannot be serviced. Replace as complete unit if malfunctioning.

• Removing and installing, refer to => [ Master Brake Cylinder ] Master Brake Cylinder.

12 Brake Line

• 18 Nm

• Master brake cylinder/secondary piston circuit to hydraulic unit. Refer to => [ On the Brake Master Cylinder ] Service and Repair.

13 Brake Line

• 18 Nm

• Master brake cylinder/primary piston circuit to hydraulic control unit. Refer to => [ On the Brake Master Cylinder ] Service and Repair.

14 Sealing Plugs

• Moisten with brake fluid and press into brake fluid reservoir.

15 Brake Fluid Level Warning Switch (F34)

16 Stud Bolt

• 8 Nm

17 Cap

18 Brake Fluid Reservoir

19 Pressure Sensor

• Brake booster pressure sensor (G294) , hybrid

• Vacuum sensor (G608) , V8 FSI

20 Vacuum Hose

• Insert into brake booster.

21 Sealing Plugs

• Connection for vacuum hose.