(Brake Master Cylinder, Location/Task/Design/Function - GF42.10-P-3100GG)
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
Location
The master brake cylinder is located in the left rear of the engine compartment on the brake unit.
Design of master brake cylinder (vehicles without antilock braking system (ABS))
Task
To generate brake force for the wheel brakes with the aid of brake fluid.
Design of master brake cylinder (vehicles with ABS)
The master brake cylinder is equipped with a secondary piston with integrated central valve, whereby the communication bore in the secondary brake circuit has been discontinued. This function is assumed by the central valve.
The central valve means that during brake pressure buildup, the primary cup of the primary piston cannot be damaged at the communication bore by pressure surges that are generated by ABS control actions.
| Function | Vehicles with ABS: The secondary piston which has a longitudinal slot is routed by means of a spring pin into the cylinder bore. The spring pin acts as an end stop for the secondary piston, for opening the central valve and simultaneously a replenishing port. When the primary piston is actuated the primary cup 2 moves over the communication bore first. After this the secondary piston is moved forward by the pressure buildup, whereby the central vale, consisting of valve spring, valve seal and valve pin, closes. Both pressure chambers are now closed, and the necessary brake pressure can be built up. When the brake pedal is released the two pistons, secondary piston and the primary piston are pushed back by the compression spring's application force, whereby the valve pin runs along the spring pin acting as an end stop and opens the central valve. The pressure and volume control surge can then take place. |