Checking brake booster - AR43.10-P-0325GZ

MODEL 164

Fig 1: Checking Brake Booster

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Illustrated on model 164.175

	Checking
	Risk of poisoning caused by swallowing brake fluid. Risk of injury caused by brake fluid coming into contact with skin and eyes.	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
	Notes on repairs to brake system		AH42.00-P-0003-01A
	Risk of death caused by vehicle slipping or toppling off of the lifting platform.	Align vehicle between columns of vehicle lift and position four support plates at vehicle lift support points specified by vehicle manufacturer.	AS00.00-Z-0010-01A
1	Open engine hood and raise to vertical position		AR88.40-P-1000GZ
2	Connect vacuum tester (1) to brake booster (3).	Observe manufacturer's operating instructions in order to prevent erroneous measurement or faulty operation! Reduce vacuum of brake pedal beforehand by pressing pedal several times.	AR43.10-P-0024-01GZ
		Test connection	Figure
		Vacuum tester	Figure
3	Connect brake fluid replacement unit	Observe manufacturer's operating instructions! Brake fluid changer
4	Raise vehicle using two-post lift	Only lift vehicle until wheels have sufficient ground clearance. Two-post	AR00.60-P-1000GZ
5	Take off left front wheel
	Remove/install wheels, rotate if necessary		AP40.10-P-4050Z
6	Remove bleed screw from floating brake caliper (7) and connect pressure tester (6).	Pressure testers for hydraulic oil systems should not be used for systems with brake fluid otherwise the brake fluid will be mixed with mineral oil which can then lead to brake failure. Observe manufacturer's operating instructions in order to prevent erroneous measurement or faulty operation! Collect escaping brake fluid.
7	Bleed pressure tester (6) using brake fluid changer	Observe manufacturer's operating instructions in order to prevent erroneous measurement or faulty operation!
8	Switch off brake fluid changer and release pressure	Brake fluid changer
9	Install pedal force meter	Observe manufacturer's operating instructions in order to prevent erroneous measurement or faulty operation! Install pedal force meter sensor (4) at brake pedal and set up pedal force meter display unit (5) so that it can be seen. Pedal force meter
	Risk of accident caused by vehicle starting off by itself when engine is running. Risk of injury caused by contusions and burns during starting procedure or when working near the engine as it is running	Secure vehicle to prevent it from moving by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.	AS00.00-Z-0005-01A
10	Start engine and create a vacuum of 0.75 to 0.80 bar by accelerating and then suddenly releasing the accelerator pedal.	If only a substantially lower vacuum is attained or if the vacuum immediately falls away, the O-ring between the brake booster and the tandem master brake cylinder may be damaged or the vacuum line with check valve (2) may be defective: ↓
		Checking check valve	AR43.10-P-0023GZ
		Remove/install stepped tandem brake master cylinder, install new O-ring.	AR42.10-P-0310GZ
11	Apply five specified brake pedal forces to brake pedal in succession	Read off and note the relevant measured values of the brake line pressure on the low pressure gauge or on the high pressure gauge of the pressure tester (6). Measured values must be within specified ranges. With each measurement, ensure that a vacuum of 0.75 to 0.80 bar is maintained.	*BE43.10-P-1002-01E
		Test connection	Figure
		Vacuum tester Pedal force meter Pressure tester	Figure
12	Turn off engine
13	Remove pedal force meter	-
14	Detach pressure tester (6) and screw bleed screw into floating brake caliper (7) again	Collect escaping brake fluid. - -
15	Bleed brake system	After the test only bleed the floating brake caliper (7) to which the pressure tester (6) was connected. Observe manufacturer's operating instructions!	AR42.10-P-0010GZ
		Bleed screw to brake caliper - -	*BA42.10-P-1001-10L
16	Install left front wheel
	Remove/install wheels, rotate if necessary		AP40.10-P-4050Z
17	Lower vehicle		AR00.60-P-1000GZ
		-
18	Detach brake fluid replacement unit	-
19	Disconnect vacuum tester (1) from brake booster (3)		AR43.10-P-0024-01GZ
		Test connection	Figure
		Vacuum tester	Figure
20	Close engine hood		AR88.40-P-1000GZ

PNEUMATIC BRAKE BOOSTER TEST SPECIFICATIONS

Number	Designation					Model 164.1/8
BE43.10-P-1002-01E	Brake pipe line pressure	Intake manifold vacuum	Force on brake pedal	50 N	bar	26.5...32
		0.75...0.8 bar		100 N	bar	50...57
				150 N	bar	72...82
				200 N	bar	95...107
				250 N	bar	118...124

FRONT AXLE BRAKE CALIPER

Number	Designation		Model 164 except 164.177	Model 164.177
BA42.10-P-1001-10L	Bleed screw to brake caliper	Nm	18	18

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

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 3: Identifying Vacuum Tester (201 589 13 21 00)

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.