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Home >> Mercedes Benz >> 2021 >> E53 AMG 2D Convertible >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Brakes - Pneumatic System - 238 Chassis >> Testing & Repair >> Checking Brake Booster - AR43.10-P-0325LWO

Checking Brake Booster - AR43.10-P-0325LWO

Model 238 

G15378071Courtesy of MERCEDES-BENZ USA
G15378072Courtesy of MERCEDES-BENZ USA
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
Notice  Brake fluid notes   AH42.50-P-0001-01A
REMOVING Remove     
1 Remove both wiper arms   AR82.30-P-6100LW
2 Remove cover (1) on the driver side    
3 Remove cover (1) on the passenger side    
4 Remove air-water-duct under the wiper arms    
5 Remove strut (2)    
6 Clean area surrounding cap on brake fluid reservoir NOTES
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 
7 Unscrew cap from brake fluid reservoir    
8 Remove front wheel on the driver side   AR40.10-P-1102A
INSPECT Check     
9 Connect filling unit to brake fluid reservoir    
REFER TO SPECIAL TOOLS 000 588 01 82 00 Filling unit   WS25.00-P-0016B
REFER TO CAPACITIES & SPECIFICATIONS General brake fluid   BB00.40-P-0330-01A
REFER TO CAPACITIES & SPECIFICATIONS Brake fluids (DOT 4 plus)   BB00.40-P-0331-00A
10 Reduce vacuum in BAS brake booster (A7/7) by depressing brake pedal several times    
11 Connect vacuum tester (4) with test connection (5) to BAS brake booster (A7/7)   AR43.10-P-0024-01LWO 
    SPECIAL TOOL Tester Fig 2
    SPECIAL TOOL Test connection Fig 1
12 Unscrew vent screw from front brake caliper on the driver side and connect test equipment (7)    
REFER TO SPECIAL TOOLS 000 588 07 21 00 Test equipment NOTES
Use correct connection fitting (pitch, cone etc.).
Leaks and measurement errors can otherwise occur.
WS42.00-P-0014B
13 Bleed test equipment (7)    
14 Connect pedal force meter (8) to brake pedal IMPORTANTCommercially available devices/tools 
Pedal force meter (8)
 
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
15 Start the engine and generate specified vacuum IMPORTANT If this vacuum is not reached or it drops immediately, the seal between the BAS brake booster (A7/7) and master brake cylinder may be damaged or the check valve (6) in the vacuum line (3) may be defective.
HAND-HELD TESTER Brake line pressure
If the specified vacuum is not reached
↓
Switch off engine and check the check valve (6).
*BE43.10-P-1004-01G 
      AR43.10-P-0023LW 
16 Replace seal between BAS brake booster (A7/7) and master brake cylinder If the specified vacuum has not been reached or if it drops off straight away and the check valve (6) is not defective. AR42.10-P-0300LWO
17 Apply the specified force to the brake pedal and read off the line pressure on the test equipment (7) HAND-HELD TESTER Brake line pressure
If line pressure is not reached
↓
Replace BAS brake booster (A7/7).
*BE43.10-P-1004-01G 
      AR43.10-P-0350LWO 
18 Turn off engine    
19 Remove pedal force meter (8) from brake pedal    
20 Disconnect vacuum tester (4) with test connection (5) from BAS brake booster (A7/7)   AR43.10-P-0024-01LWO 
21 Disconnect test equipment (7) with connection fitting and screw in vent screw at brake caliper on the driver side all the way    
22 Bleed brake caliper on the driver side   AR42.10-P-0010-02LWE
    TORQUE SPECIFICATION Bleed screw at brake caliper *BA42.10-P-1003-10X 
23 Disconnect filling unit from brake fluid reservoir    
24 Check and correct fluid level in the brake fluid reservoir    
REFER TO MAINTENANCE     AP42.10-P-4210B
INSTALLING Install     
25 Mount front wheel on the driver side   AR40.10-P-1102A
26 Seal brake fluid reservoir using cap    
27 Install strut (2) TORQUE SPECIFICATION Screw/bolt, lower strut to suspension strut tower mounting bracket *BA62.30-P-1003-02K 
    TORQUE SPECIFICATION Screw/bolt, lower strut to firewall *BA62.30-P-1004-02K 
28 Install air-water-duct under the wiper arms    
29 Install cover (1) on the passenger side    
30 Install cover (1) on the driver side    
31 Install both wiper arms   AR82.30-P-6100LW
CHECK VALUES FOR PNEUMATIC BRAKE BOOSTER

Number Designation Model 238
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 238 (except 238.361/461) Model 238.361/461
BA42.10-P-1003-10X Bleed screw at brake caliper Nm 14 14
FROND END WITH FRONT REINFORCEMENT

Number Designation Model 238
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 238
BA62.30-P-1004-02K Screw/bolt, lower strut to firewall Nm 23
Fig 1: Identifying Test Connection (168 589 08 63 00)
G15378073Courtesy of MERCEDES-BENZ USA
Fig 2: Identifying Tester (201 589 14 21 00)
G14791024Courtesy of MERCEDES-BENZ USA
REPAIR MATERIALS

Number Designation Order number
BR00.45-Z-1028-04A Assembly cleaner A 000 986 56 01