Brake Booster and Master Cylinder Overview

Brake Booster and Master Cylinder Overview

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






1 Pedal Assembly

2 Self-Locking Nut

• 25 Nm

• Always replace if removed.

3 Gasket

• For brake booster

4 Brake Booster

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

• Some vehicles with gasoline engine and automatic transmission are equipped with a Brake System Vacuum Pump (V192) => [ Brake System Vacuum Pump (V192) ] Service and Repair.

• On vehicles with a hydraulic brake booster, a vacuum sensor is installed, refer to => [ Brake Booster Vacuum Sensor (G483) ] Brake Booster Vacuum Sensor (G483)

• Functional check:

- With engine switched off, depress brake pedal firmly several times (to deplete vacuum in tool).

- 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.

5 Seal

6 Brake Booster Vacuum Sensor (G483)

• Only on vehicles with the hydraulic brake booster.

• Removing and Installing, refer to => [ Brake Booster Vacuum Sensor (G483) ] Brake Booster Vacuum Sensor (G483).

7 Brake Master Cylinder without Brake Lamp Switch

• Allocation, refer to the Parts Catalog.

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

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

8 Brake Master Cylinder with Brake Lamp Switch

• Allocation, refer to the Parts Catalog.

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

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

9 Brake Lamp Switch (F)

• Includes brake pedal switch (F47)

• On vehicles through calendar week 45/05, the brake lamp switch (F) is located on the brake pedal, refer to => [ Brake Pedal Overview ] Brake Pedal Overview.

• Removing and Installing, refer to => [ Brake Lamp Switch (F) 07 November 2005 ] Brake Lamp Switch (F) 07 November 2005.

10 Inner TORX(R) Bolt

• 5 Nm

11 Heat Shield

12 Self-Locking Nut

• 25 Nm

• Always replace if removed.

13 Brake Line

• 14 Nm

• Master brake cylinder/secondary piston circuit to hydraulic unit.

14 Brake Line

• 14 Nm

• Master brake cylinder/primary piston circuit to hydraulic control unit.

15 Sealing Plug

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

16 Brake Fluid Reservoir

17 Cap

18 Sealing Plug

• Connection for vacuum hose.

19 Vacuum Hose

• Insert into brake booster.

20 Brake Booster Pressure Sensor (G294)

• On vehicles with FSI engine without Hydraulic Brake Vacuum Booster.

• Removing and Installing, refer to => [ Brake Booster Pressure Sensor (G294) ] Brake Booster Pressure Sensor (G294).