(Function Of Brake Vacuum System - GF43.10-P-3001GG)

MODEL 460, 

461.217/219/227/229/238/239/249/266/267/302/321/322/323/326/327/328/329/331/332/335/336/337/338/341/342/345/365/366/367/368/392/401/402/403/404/405/450/451/452/454/455/456/458/459, 463 up to 5/31/12 

Schematic diagram 

Courtesy of MERCEDES-BENZ USA

General function 

In case of diesel engines, the vacuum required for the brake assistant is generated by a vacuum pump (48). In case of gasoline engines, the intake manifold vacuum is used for brake servo assistance.

The vacuum pump (48) is installed at the timing case cover and is driven via the cams at the injection timing device.

From the vacuum pump (48), the vacuum reaches the brake unit (5) via a line. At the same time, the vacuum is also stored in vacuum reservoirs (15, 15a). The volume is increased through these vacuum reservoirs (15, 15a) and multiple brake applications can be carried out consecutively without causing the brake servo assistance to be reduced.

A check valve (41) is installed in the vacuum line of the vacuum pump (48) for brake unit (5). The check valve (41) has the task of keeping the vacuum in the brake unit (5) constant and storing it. If the vacuum pump (48) is defective, the check valve (41) also prevents the ingress of engine oil into the brake unit (5).

The brake unit (5) has a vacuum fitting and a connection for outside air (atmospheric pressure). The pressure differential between the two pressures is used for pedal force support at the brake pedal. In case of loss of vacuum, the system continues to work like a normal hydraulic braking system. In that case, a correspondingly higher pedal force is required for braking.

The master brake cylinder is flange-mounted directly on the brake unit (5) and is operated by the brake unit (5) via a push rod.