Checking brake booster

AR43.10-P-0325EQ

Checking brake booster

06.03.2020

Model

293

1

Brake booster

3

Strut

2

Cover

030

Vacuum tester

031

Test connection

051

Tester

060

Pedal force meter

1

Brake booster

8

Vacuum line

17

Check valve

 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

Brake fluid notes

AH42.50-P-0001-01A

Notes on safety-relevant components

AH00.00-Z-0019-01A



Remove

1

Remove both wiper arms.

2

Remove cover (2).

3

Remove air/water duct under the wiper arms.

4

Remove strut (3).

5

Clean area surrounding cap at brake fluid reservoir.


Before opening, clean the areas surrounding the cap thoroughly.
Otherwise particles of dirt in the hydraulic components can result in malfunctions and total failure of the brake system.

Assembly cleaner

*BR00.45-Z-1028-04A

6

Open brake fluid reservoir at cap.



Check

7

Connect filling unit to brake fluid reservoir.



000 588 01 82 00 Filling unit

WS25.00-P-0016B



General brake fluid

BB00.40-P-0330-01A



Brake fluids (DOT 4 plus)

BB00.40-P-0331-00A

8

Reduce vacuum in brake booster (1) by depressing the brake pedal several times.

9

Connect vacuum tester (030) with test connection (031) to brake booster (1).

AR43.10-P-0024-01V

 Test connection

*168589086300

 Vacuum tester

*201589132100

10

Raise vehicle.

AR00.60-P-1006A

11

Remove vent screw at front brake caliper on driver's side and connect test equipment (051).



000 588 07 21 00 Test equipment

WS42.00-P-0014B


Use correct connection fitting (pitch, centering cone, etc.).
Leaks and measurement errors can otherwise occur.

12

Bleed test equipment (051).

13

Connect pedal force meter (060) at brake pedal.



000 588 05 21 00 Roller brake test stand

WS42.00-P-0006B

14

Start the engine and generate specified vacuum.

 If this vacuum is not reached or immediately drops, the seal between the brake booster (1) and the master brake cylinder may be damaged or the check valve (17) in the vacuum line (8) may be defective.

Brake line pressure

*BE43.10-P-1004-01G

If the specified vacuum is not reached



Switch off engine and check the check valve (17).

AR43.10-P-0023EQ

15

Replace seal between brake booster (1) and master brake cylinder.

If the specified vacuum has not been reached or falls immediately and the check valve (17) is not defective.

AR42.10-P-0300EQ

16

Apply specified force to brake pedal and read off line pressure on test equipment (051).

Brake line pressure

*BE43.10-P-1004-01G

If line pressure is not reached



Replace brake booster (1).

AR43.10-P-0350EQ

17

Switch off engine.

18

Remove pedal force meter (060) from brake pedal.

19

Disconnect vacuum tester (030) with test connection (031) from brake booster (1).

AR43.10-P-0024-01V

20

Disconnect test equipment (051) with connection fitting and screw in vent screw at brake caliper of driver's side up to end stop.

21

Bleed brake caliper on the driver's side.

AR42.10-P-0010-02LW

 Bleed screw at brake caliper

*BA42.10-P-1003-10W

22

Lower vehicle.

AR00.60-P-1006A

23

Disconnect filling unit from brake fluid reservoir.

24

Check and correct fluid level in brake fluid reservoir.



AP42.10-P-4210F



Install

25

Seal brake fluid reservoir with cap.

26

Install strut (3).

 Screw/bolt, lower strut to suspension strut tower mounting bracket

*BA62.30-P-1003-02K

 Screw/bolt, lower strut to firewall

*BA62.30-P-1004-02K

27

Install air/water duct under the wiper arms.

28

Install cover (2).

29

Install left and right wiper arms.

AR82.30-P-6100LW

Check values for pneumatic brake booster

Number

Designation

Model 293

BE43.10-P-1004-01G

Brake line pressure

Vacuum 0.92…0.98 bar

Force on brake pedal

50 N

bar

22

100 N

bar

41

150 N

bar

61

200 N

bar

80

250 N

bar

100

 Front axle brake caliper

Number

Designation

Model 293

BA42.10-P-1003-10W

Bleed screw at brake caliper

Nm

14

 Frond end with front reinforcement

Number

Designation

Model 293

BA62.30-P-1003-02K

Screw/bolt, lower strut to suspension strut tower mounting bracket

Nm

50

 Frond end with front reinforcement

Number

Designation

Model 293

BA62.30-P-1004-02K

Screw/bolt, lower strut to firewall

Nm

23

Repair materials

Number

Designation

Order number

BR00.45-Z-1028-04A

Assembly cleaner

A 000 986 56 01