Hydraulic Unit and Brake Booster/Brake Master Cylinder Assembly Overview

Hydraulic Unit and Brake Booster/Brake Master Cylinder Assembly Overview






1 ABS Control Module (w/EDL) (J104)

• Component location: In right engine compartment below engine control module.

Disconnecting ABS Control Module and ABS Hydraulic Unit is not permitted.

2 ABS Hydraulic Unit (N55)

• Component location: in right engine compartment below engine control module.

3 Brake Line

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

• Identification at hydraulic unit - DK -.

4 Brake Line

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

• Identification at hydraulic unit - SK -.

5 Brake Line

• Via intermediate piece toward rear left brake caliper.

• Marked on hydraulic unit with - HL -.

6 Brake Line

• Via intermediate piece toward front right brake caliper.

• Marked on hydraulic unit with - VR -.

7 Brake Line

• To left front brake caliper.

• Marked on hydraulic unit with - VL -.

8 Brake Line

• Via intermediate piece toward rear right brake caliper.

• Marked on hydraulic unit with - HR -.

9 Intermediate Piece

10 Bracket

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

11 Bolt

• 5 Nm

12 Bolt

• 8 Nm

13 Buffer

14 Gasket

• For brake booster.

15 Brake Booster

• Removing and installing => [ Brake Booster ] Brake Booster

• Component location: in engine compartment, left.

• 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).

16 Brake Booster Membrane Position Sensor

• Removal is not intended.

17 Sealing Plugs

• Connection for vacuum hose.

18 Vacuum Hose

• Insert into brake booster.

19 Seal

20 Nut

• Self-locking

• 49 Nm

• Always replace after removal.

21 Bracket

22 Brake Master Cylinder

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

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

23 Sealing Plugs

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

24 Brake Fluid Reservoir

25 Cap

• With float warning indicator sensor.

Brake Lines from Brake Master Cylinder, Connecting to Hydraulic Unit






A Hydraulic unit to primary piston circuit of master brake cylinder.
Identification at hydraulic unit - DK -.
B Hydraulic unit to master cylinder secondary piston circuit.
Identification at hydraulic unit - SK -.
1 Hydraulic unit to front left brake caliper.
Marked on hydraulic unit with - VL -.
2 Hydraulic via intermediate unit to front right brake caliper.
Marked on hydraulic unit with - VR -.
3 Hydraulic via intermediate unit to rear right brake caliper.
Marked on hydraulic unit with - HR -.
4 Hydraulic via intermediate unit to rear left brake caliper.
Marked on hydraulic unit with - HL -.