REMOVING AND INSTALLING BRAKE BOOSTER WITH TANDEM BRAKE MASTER CYLINDER Brake Booster Type 52/4/255 Checking Function: Operate brake pedal 10 times with the engine stopped. Hold brake pedal down and start the engine. If the brake pedal does not give, there could be a fault in the check valve, vacuum hose or rubber ring between the tandem brake master cylinder and brake booster, or the engine vacuum supply could be insufficient or the filter cartridge of the brake booster could be completely clogged. Checking Engine Vacuum for Brake Booster: Disconnect vacuum hose on brake booster. Install vacuum tester, Special Tool 34 3 100, between brake booster and check valve. Check vacuum while releasing the accelerator, beginning at an engine speed of 3000 rpm and with the engine at operating temperature. Minimum value: - 0.35 bar. Repeat this test several times. Minimum value for specified idle speed and engine with operating temperature = - 0.50 bar. |  |
Draw off brake fluid in tank with a syringe reserved exclusively for use with brake fluid. Pull off plug. Pull off clutch hydraulic hose (1). |  |
Unscrew brake pipes (2 and 3). Brake pipes (2) (1st brake circuit) front left front right Brake pipe (3) (2nd brake circuit) rear right rear left |  |
Remove dashboard trim panel at bottom left - see Gr. 51. Disconnect spring. Press off clip (3) and pull out pin (4).  51 45 000
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If the brake booster´s filter cartridge is completely clogged, remove cap (1), holder (2), damper (3) and filter (4). Installation: Clean damper (3) and filter (4). Offset slots of damper (3) and filter (4) by 180° to each other. Basic adjusted distance A on piston rod = 125 mm. Adjust brake pedal - see Gr. 35. 35 21 000
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