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

Model 171, 172, 217, 222, 231 

Modification notes 

Illustrated on model 203 

Courtesy of MERCEDES-BENZ USA

	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
	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
	Brake fluid notes		AH42.50-P-0001-01A
	Check
1	Depress brake pedal several times with engine switched off to reduce the vacuum in the BAS brake booster (A7/7)
2	Open engine hood and raise to vertical position	Model 171, 172, 217, 222, 231 Model 171, 172	AR88.40-P-1000V
3	Connect vacuum tester (030) with test connection (031) to BAS brake booster (A7/7)		AR43.10-P-0024-01V
		Model 172	*BE43.10-P-1002-01F
		Model 217 Model 222 except code Z07 (Top protection) Model 231 Boost factor Model 172	*BE43.10-P-1001-01F
		Model 217 Model 222 except code Z07 (Top protection) Model 231 Brake booster Ø Model 171 Boost factor	*BE43.10-P-1002-01A
		Model 171 Brake booster Ø	*BE43.10-P-1001-01A
		Vacuum tester	Fig 1
		Test connection	Fig 2
4	Connect pressure tester (051) with connection fitting to brake caliper	Use correct connection fitting (pitch, cone etc.). Leaks and measurement errors can otherwise occur. MODEL 217, 222 Bleed screw on brake caliper	*BA42.10-P-1002-10V
		Model 171 (except 171.473) Model 171.473 Bleed screw to brake caliper	*BA42.10-P-1002-12P
		Model 171 Bleed screw to brake caliper	*BA42.10-P-1002-10P
		MODEL 231 Bleed screw on brake caliper	*BA42.10-P-1005-10U
		Model 172, 217, 222, 231 Bleed screw to brake caliper	*BA42.10-P-1002-12J
		Model 172 Bleed screw at brake caliper	*BA42.10-P-1003-10J
6	Start engine and by opening the throttle, produce a vacuum of 0.75 to 0.80 bar	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 (17) in the vacuum line (8) may be defective. In this case: ↓ Check non-return valve.	AR43.10-P-0023V
7	Replace seal between BAS brake booster (A7/7) and master brake cylinder	If a vacuum of 0.75 to 0.80 bar is not reached or drops immediately and the check valve (17) is not defective. Model 217, 222	AR42.10-P-0300LF
		Model 171	AR42.10-P-0310V
		Model 172	AR42.10-P-0300CW
		Model 231	AR42.10-P-0300RK
8	Apply the specified force to the brake pedal and read off the line pressure on the pressure tester (051)	In order to cover measurement errors (incorrect force on the brake pedal, incorrect vacuum) and scatter of the measuring devices, a tolerance of ± 10 bar on the specified value is permissible. The measured value must be within the value range. Model 172 Model 217 Model 222 except code Z07 (Top protection) Model 231 Brake line pressure	*BE43.10-P-1003-01F
		Model 171 Brake pipe line pressure	*BE43.10-P-1003-01A
9	Detach vacuum tester (030) with test connection (031) from BAS brake booster (A77)
10	Detach pressure tester (051) with connection fitting from brake caliper
11	Remove pedal force meter (060) from brake pedal
12	Bleed brake system	Model 217, 222	AR42.10-P-0010LF
		Model 231	AR42.10-P-0010RK
		Model 171	AR42.10-P-0010V
		Model 172 Only bleed the brake caliper to which the pressure tester (051) was connected.	AR42.10-P-0010CW
	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
13	Check brake system for leaks		AR42.10-P-0100-01V

Fig 1: Identifying Vacuum Tester (201 589 13 21 00)

Courtesy of MERCEDES-BENZ USA

Fig 2: Identifying Test Connection (168 589 08 63 00)

Courtesy of MERCEDES-BENZ USA