Vacuum Brake Booster: Locations

Tandem brake booster / brake master cylinder, assembly overview

Note:
^ Brake master cylinders can no longer be disassembled, i.e. no provision is made for servicing.
^ Use only new brake fluid. Observe information on brake fluid reservoir!
^ Assignment of brake line connections





1 - - a - Vacuum hose
^ On gasoline engines the vacuum required is taken from the intake manifold and/or a mechanical vacuum pump.
^ Insert into brake booster unit

1 - - b - Vacuum hose
^ On gasoline engines the vacuum required is taken from the intake manifold and/or a mechanical vacuum pump.
^ An additional electrical vacuum pump is installed on vehicles where vacuum is taken from intake manifold only
^ Insert into brake booster unit

2 - Trunnion bolt, 8 Nm
^ Screw in as far as stop
^ Unscrew to remove brake fluid reservoir

3 - Brake fluid reservoir with float warning indicator
^ Functional test
^ With the ignition switched on, remove filler cap and press with your hand on the strainer that is visible in the reservoir. Warning lamp in instrument cluster should light up and acoustic alarm should sound.
^ Refer to label on reservoir before topping off brake fluid

4 - Filler cap

5 - Sealing plug
^ Moisten with brake fluid and insert into brake master cylinder
^ Press brake fluid reservoir into sealing plugs

6 - Brake booster
^ Adjusting ball head
^ Functional check
^ With the engine switched off, firmly depress the brake pedal several times (this reduces the vacuum present in the servo unit).
^ Then hold brake pedal in applied position with moderate force and start engine. If the servo unit is working properly, the pedal will give slightly under foot (servo assist becomes activated).
^ If faulty replace complete.

7 - Pedal bracket

8 - Supply hose
^ Keep both ends closed off until it is installed.
^ Push on hose as far as it will go.

9 - Bulkhead

10 - Bolt, 25 Nm

11 - Collar nut, 50 Nm
^ Always replace

12 - Brake master cylinder
^ Cannot be repaired. If faulty, replace complete.
^ Has to be removed and installed together with the brake booster unit.

13 - Brake line, 15 Nm
^ Brake master cylinder/primary piston circuit to hydraulic unit
^ Brake master cylinder/secondary piston circuit to hydraulic unit

14 - Sealing ring
^ Insert into groove on brake master cylinder
^ Replace after removing brake master cylinder