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

Fig 1: Identifying Brake Booster

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. See AS42.50-Z-0001-01A

Brake fluid notes. See AH42.50-P-0001-01A

Eliminate the vacuum in brake booster (A7/7). To do this, press the brake pedal several times with the engine switched off.

Open engine hood and raise to vertical position.

Connect vacuum tester (030) to brake booster (A7/7) with test connection (031). See AR43.10-P-0024-01V . Test specifications for brake booster. See BE43.10-P-1001-01F and BE43.10-P-1002-01F . Special tools 201589132100 168589086300, see Fig 2.

Connect pressure tester (051) with connection fitting to brake caliper. Use the correct connection fitting (pitch, taper etc.), otherwise leakage and measurement errors will occur.

Start engine and by opening the throttle produce a vacuum of 0.75 to 0.8 bar. If this vacuum is not reached or it drops immediately, the seal between the brake booster (A7/7) and master brake cylinder may be damaged or the check valve (17) in the vacuum line (8) may be defective: Check non-return valve. Remove/install master brake cylinder, replace gasket: See AR42.10-P-0300CW

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. Brake pipe line pressure. See BE43.10-P-1003-01F .

Detach vacuum tester (030) with test connection (031) from brake booster (A7/7). Detach pressure tester (051) with connection fitting from brake caliper

Remove pedal force meter (060)

Bleed brake system. Only bleed the brake caliper to which the pressure tester (051) was connected. See AR42.10-P-0010CW

Secure vehicle to prevent it from moving by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts. See AS00.00-Z-0005-01A and AR42.10-P-0100-01V .

PNEUMATIC BRAKE BOOSTER TEST SPECIFICATIONS

Number	Designation		Model 204
BE43.10-P-1001-01F	Brake booster dia.	mm	203/203
	Brake booster dia.	inch	8/8
BE43.10-P-1002-01F	Boost factor	-	≈5,6
BE43.10-P-1003-01F	Brake pipe line pressure. Intake manifold vacuum 0.75...0.8 bar. Force on brake pedal	50 Nm bar	16.7...23.7
		100 N bar	33.3...42.9
		150n bar	49.8...61.4
		200n bar	66.3...79.8
		250n bar	82.9...98.3

FRONT AXLE BRAKE CALIPER

Number	Designation	Model 204
BE43.10-P-1002-01F	Bleed screw to brake caliper	14 Nm

Fig 2: Vacuum Tester (201 589 13 21 00) And Test Connection (168 589 08 63 00)