Remove/install brake booster

AR43.10-P-0350RT

Remove/install brake booster

12.02.2019

Model

251

Modification notes

01.09.2010

"Perform brake test on test bench" reference changed

Test sequence augmented/revised

1

Safety clip

2

Pin

3

Nuts

4

Wiper arms

5

Water deflector

6

Wiper system

7

Partition wall between wheel well liners

8

Vacuum line

9

Indicator switch connector coupling

10

Diaphragm travel sensor connector

A7/7

BAS brake booster

H3

Alarm signal horn

 

Remove/install

 Caution

Risk of poisoning from swallowing brake fluid. Risk of injury from skin and eye contact with brake fluid

Only pour brake fluid into suitable and appropriately marked containers. Wear protective clothing and eye protection when handling brake fluid.

AS42.50-Z-0001-01A

Topical note

Notes on externally invisible brake fluid loss

AH42.10-P-9406-02A

Topical note

Brake fluid notes

AH42.50-P-0001-01A

Topical note

Notes on repairs to brake system

AH42.00-P-0003-01A

1

Move wiper arms to end position (4)

2

Drive back driver's seat

3

Switch off ignition and remove the transmitter key from the EIS [EZS] control unit

 On vehicles with code 889 Keyless-Go: Press Keyless-Go start/stop button repeatedly until the ignition is switched off. Remove transmitter key from vehicle and store it at a location beyond its transmission range (at least 2 m).

4

Eliminate vacuum in BAS brake booster (A7/7)

 Relieve vacuum by depressing the brake pedal several times.

5

Unlock engine hood

 The hood can no longer be unlocked after removal of the cover under the instrument panel (left).

6

Remove left cover under the dashboard

AR68.10-P-1500RT

7

Remove safety clip (1) and pull out bolt (2)

8

Unscrew nuts (3) of BAS brake booster (A7/7)

 Nut from brake booster carrier to front end

*BA43.10-P-1001-01H

9

Open engine hood and raise to vertical position

AR88.40-P-1000RT

10

Remove wiper arms (4)

AR82.30-P-6100RT

11

Remove water drain (5) above windshield wiper system (6)

AR83.25-P-1406RT

12

Remove windshield wiper system (6)

AR82.30-P-6400RT

 Bolt on wiper motor

*BA82.30-P-1002-01K

 Bolt, window wiper frame to body

*BA82.30-P-1004-01K

13

Remove partition between wheel wells (7)

AR62.30-P-2400RT

 Bolt, partition wall between wheel well liners to wheel well liners

*BA62.30-P-1007-01E

14

Remove stepped tandem brake master cylinder

AR42.10-P-0310RT

 Brake pipe to master brake cylinder

*BA42.10-P-1003-14A

 Nut, brake master cylinder to brake booster

*BA42.10-P-1001-05I

 Bolt, impact deflector plate to master brake cylinder

*BA42.10-P-1002-05I

 Bolt, brake fluid reservoir to master brake cylinder

*BA42.10-P-1003-05I

 Brake pressure sensor to master brake cylinder

*BA42.45-P-1001-01K

 Box wrench bit

*140589000300

 Record plug

*129589009100

15

Remove alarm signal horn (H3)

AR80.50-P-9840RT

16

Remove vacuum line (8) from BAS brake booster (A7/7)

17

Remove indicator switch connector coupling (9)

18

Remove diaphragm travel sensor connector coupling (10)

19

Take out BAS brake booster (A7/7)

 Installation:
Do not damage boot during installation of BAS brake booster (A7/7).
To prevent leaks.

 Installation: Replace seal.

20

Install in the reverse order

21

Bleed brake system

AR42.10-P-0010RT

 Bleed screw at brake caliper

*BA42.10-P-1001-10L

 Bleed screw to brake caliper

*BA42.10-P-1001-12L

 Brake fluid

*BF42.10-P-1001-01H



Check

 Warning

Risk of accident from vehicle starting off by itself when engine running. Risk of injury (bruises and burns) resulting from working on the engine while it is being started or when it is running.

Secure vehicle to prevent it from starting off by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.

AS00.00-Z-0005-01A

22

Check brake system for leaks

AR42.10-P-0100-01RT

 Danger

Risk of death caused by limbs being caught or crushed by rotating parts when performing tests on the brake test stand

Never leave the vehicle unattended on the rollers except in an emergency. Ensure that no one is under the vehicle or near rotating parts during testing. In case of emergency, use the EMERGENCY OFF switch to shut down test stand.

AS42.00-Z-0001-01A

23

Carry out brake test on the test stand



AP42.00-P-4290BA

 Master brake cylinder

Number

Designation

Model 251

BA42.10-P-1001-05I

Nut, brake master cylinder to brake booster

Nm

25

 Front axle brake caliper

Number

Designation

Model 251 (except 251.077/177)

Model 251.077/177

BA42.10-P-1001-10L

Bleed screw at brake caliper

Nm

18

18

 Rear axle brake caliper

Number

Designation

Model 251

BA42.10-P-1001-12L

Bleed screw to brake caliper

Nm

7

 Master brake cylinder

Number

Designation

Model 251

BA42.10-P-1002-05I

Bolt, impact deflector plate to master brake cylinder

Nm

14

 Master brake cylinder

Number

Designation

Model 251

BA42.10-P-1003-05I

Bolt, brake fluid reservoir to master brake cylinder

Nm

4

 Brake hoses, brake lines

Number

Designation

Model 251

BA42.10-P-1003-14A

Brake pipe to master brake cylinder

Nm

18

 Electronic Stability Program (ESP)

Number

Designation

Model 251

BA42.45-P-1001-01K

Brake pressure sensor to master brake cylinder

Nm

35

 Brake booster

Number

Designation

Model 251

BA43.10-P-1001-01H

Nut from brake booster carrier to front end

Nm

25

 Crossmember and front reinforcement

Number

Designation

Model 251

BA62.30-P-1007-01E

Bolt, partition wall between wheel well liners to wheel well liners

Nm

23

 Windshield wiper

Number

Designation

Model 251

BA82.30-P-1002-01K

Bolt on wiper motor

Nm

10

 Windshield wiper

Number

Designation

Model 251

BA82.30-P-1004-01K

Bolt, window wiper frame to body

Nm

20

 Brake fluid

Number

Designation

Model 251

BF42.10-P-1001-01H

Brake fluid

Filling capacity

Liter

0,8

Sheet

BB00.40-P-0330-01A

Sheet

BB00.40-P-0331-00A