Hydraulic Unit and Brake Booster/Master Cylinder Assembly Overview
Hydraulic Unit and Brake Booster/Master Cylinder Assembly Overview
1 Anti-lock Brake System (ABS) control module (w/Electronic Differential Lock (EDL)) (J104)
2 ABS hydraulic unit (N55)
3 Brake line
• Brake master cylinder/primary piston circuit to hydraulic control unit.
• Identification at hydraulic unit - DK -.
4 Brake line
• Brake master cylinder/secondary piston circuit to hydraulic unit.
• Identification at hydraulic unit - SK -.
5 Brake line
• Via intermediate piece toward left rear brake caliper.
• Marked on hydraulic unit with - HL -.
6 Brake line
• Via intermediate piece toward right front 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 right rear brake caliper.
• Marked on hydraulic unit with - HR -.
9 Intermediate piece
10 Bracket
• Allocation.
11 Bolt, 5 Nm
12 Bolt, 8 Nm
13 Buffer
14 Gasket
• For brake booster.
15 Tandem brake booster
• Including brake pressure release solenoid (F84) and brake pressure magnetic coil (N247) (not interchangeable).
• On gas engines, vacuum is supplied from intake manifold.
• Vehicles with gas engine and automatic transmission are equipped with a brake system vacuum pump.
• On Diesel engines, a vacuum pump is installed for vacuum creation.
• Function test:
- With engine switched off, press brake pedal firmly several times (to deplete vacuum in tool).
- Press 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.
16 Seal
17 Brake booster membrane position sensor (G420)
• Removing and installing, refer to --> [ Brake Booster Membrane Position Sensor ] Service and Repair.
• Discontinued from calendar week 48/06.
18 Snap ring
19 Sealing plugs
• Connection for vacuum hose.
20 Vacuum hose
• Insert into brake booster.
21 Seal
22 Self-locking nut, 25 Nm
• Always replace after removal.
23 Brake pressure sensor (G201)
• Removing and installing, refer to --> [ Brake Pressure Sensor 1 ] Service and Repair.
• In the Electronic Stabilization Program (ESP) unit from calendar week 48/06.
24 Bracket
25 Brake master cylinder
• Cannot be serviced. Replace as complete unit if malfunctioning.
• Removing and installing, refer to --> [ Brake Master Cylinder ] Brake Master Cylinder.
26 Sealing plugs
• Lubricate with brake fluid and press into brake fluid reservoir.
27 Brake fluid reservoir
28 Cap
29 Torx bolts, 4 Nm
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 left front brake caliper.
Marked on hydraulic unit with - VL -
2 Hydraulic unit via intermediate unit to right front brake caliper.
Marked on hydraulic unit with - VR -
3 Hydraulic unit via intermediate unit to right rear brake caliper.
Marked on hydraulic unit with - HR -
4 Hydraulic unit via intermediate unit to left rear brake caliper.
Marked on hydraulic unit with - HL -
