No braking
In the brakes off position the diaphragm of the vacuum- operated servo and valve piston are pressed against the rear end position by the return spring. The same vacuum exists on both sides of the diaphragm because an overflow valve in the diaphragm is open. The return spring of the master cylinder is forced against the rear end position. In this position both central valves are open and the brake system is kept at atmospheric pressure. A stop pin prevents the secondary piston from moving backwards and a circlip prevents the primary piston from moving backward.
The master cylinder and other hydraulic components are filled with brake fluid without pressure.
The intake and outlet valves are in an inactive position in the valve block.
