Hydraulic Unit, Brake Booster and Master Cylinder Assembly Overview
Hydraulic Unit, Brake Booster and Master Cylinder Assembly Overview
• Complete brake master cylinder and brake booster can be replaced independently.
1 Brake booster
• On gasoline engines vacuum is supplied from intake manifold.
• On vehicles with gasoline engine and automatic transmission, there is also the brake system vacuum pump (V192) installed.
• On diesel engines, a vacuum pump is installed for vacuum creation.
Function test:
• With engine switched off, depress brake pedal firmly several times (to deplete vacuum 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 assist becomes effective).
• If malfunctioning: replace as complete unit only.
• Check valve (in vacuum hose)
Function test => [ check valve. ] .
• Brake assist in brake booster
Function test => [ Brake Booster Brake Assist, Checking Function, from 12.01 ] Testing and Inspection.
• Disconnect from brake pedal => [ Brake Pedal to Brake Booster, Disconnecting and Connecting ] Brake Pedal to Brake Booster, Disconnecting and Connecting.
• Removing and installing => [ Brake Booster ] Brake Booster.
2 Cap
3 Brake fluid reservoir, left-hand drive vehicles
4 Sealing plugs
• Coat with brake fluid and press into brake fluid reservoir
5 Retaining pin
• Insert through master brake cylinder
6 Master brake cylinder, left-hand drive vehicles
• Must not be serviced. Replace as complete unit if malfunctioning.
7 Brake line, 14 Nm
• Brake master cylinder/primary piston circuit to hydraulic control unit
8 Brake line, 14 Nm
• Hydraulic control unit to left front brake caliper
9 Brake line, 14 Nm
• Hydraulic control unit to right front brake caliper
10 Brake line, 14 Nm
• Brake master cylinder/secondary piston circuit to hydraulic unit
11 ABS control module (J104)
• Do not disconnect connector from control module before vehicle self-diagnosis
12 ABS hydraulic unit (N55)
The hydraulic unit consists of the following components:
• ABS hydraulic pump (V64)
• Valve block (contains inlet and outlet valves)=> [ ABS Control Module and Hydraulic Unit ] Service and Repair
13 Bracket
14 Hex nut, 20 Nm
15 Bolts, 8 Nm
16 Bolts, internal Torx E 5, 4 Nm
17 Brake line, 14 Nm
• Hydraulic control unit to wheel cylinder/rear left brake caliper
18 Brake line, 14 Nm
• Hydraulic control unit to wheel cylinder/rear right brake caliper
19 Brake fluid reservoir, right-hand drive vehicles
20 Sealing plugs
• Coat with brake fluid and press into expansion tank
21 Bleeder valve
22 Retaining plate
• Helps secure wiring harness
23 Self-locking hex nut, 20 Nm
24 Master brake cylinder, right-hand drive vehicles
• Must not be serviced. Replace as complete unit if malfunctioning.
25 Brake pressure sensor 1 (G201)
26 Bolt
• For mounting of brake fluid reservoir to master brake cylinder
27 Seal
• Replace
28 Brake booster, right-hand drive vehicles
29 Gasket
• For brake booster
30 Self-locking hex nut, 20 Nm
31 Boot
• Check for proper seat, danger of intake noises
32 Bracket
• Secured to edge of brake booster
33 Heat shield
34 Retaining plate
• Helps secure wiring harness
35 Sealing plugs