Brake Booster and Master Brake Cylinder Overview

Brake Booster and Master Brake Cylinder Overview

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






1 Pedal Assembly

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

2 Nut

• 25 Nm

• Always replace if removed.

• Follow tightening sequence. Refer to=> [ Follow the tightening sequence ] Brake Booster.

3 Gasket

• For brake booster.

4 Brake Booster

• On gasoline engines, the required vacuum is supplied either by the intake manifold or by a mechanical vacuum pump.

• 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 as a unit in the event of malfunction (previously, check all vacuum lines).

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

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

5 Seal

6 Brake Master Cylinder

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

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

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

7 Nut

• 25 Nm

• Always replace if removed.

8 Bolt

• 5 Nm

9 Brake Light Switch (F)

• Includes Brake Pedal Switch (F47).

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

10 Brake Line

• 14 Nm

• Master brake cylinder/secondary piston circuit for the ABS hydraulic unit (N55).

• Identification: diameter 6.5 mm and tube fitting with M12 x 1 thread

11 Brake Line

• 14 Nm

• Master brake cylinder/primary piston circuit for the ABS hydraulic unit (N55).

• Identification: diameter 6.5 mm and tube fitting with M12 x 1 thread.

12 Sealing Plugs

• Connection for vacuum hose.

13 Sealing Plugs

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

14 Mounting Pin

• Push to right to remove the brake fluid reservoir.

15 Brake Fluid Reservoir

• Only use new brake fluid conforming to US-Norm FMVSS 116 DOT 4.

16 Cap

• With the brake fluid level warning switch (F34).

17 Vacuum Line

• Insert into brake booster.

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

• Check if brake booster is malfunctioning.

18 Vacuum Sensor (G608) or Brake Booster Pressure Sensor (G294)

• Vacuum sensor for vehicles with HBB (hydraulic brake booster).

• Vacuum Sensor, removing and installing, refer to=> [ Vacuum Sensor (G608) ] Vacuum Sensor (G608).

• Brake booster pressure sensor for vehicles equipped with engines and DSG transmission without HBB (hydraulic brake booster).

• Brake booster pressure sensor removing and installing, refer to=> [ Brake Booster Pressure Sensor (G294) ] Brake Booster Pressure Sensor (G294).

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