Operating principles of hydraulic brake drive (Freelander 2)

When the brake pedal is pressed, the front pushrod in the brake booster causes the primary piston of the master cylinder to move in the corresponding cylinder. This creates pressure in the primary pressure chamber and, in combination with the primary spring, causes the counteracting force of the secondary spring to be overcome, simultaneously moving the secondary piston in its cylinder.

The initial movement of the pistons away from the stops closes the primary and secondary central valves located inside the master cylinder. Further movement of the pistons then causes fluid pressure to build up in the primary and secondary chambers and brake circuits. The fluid in the chambers behind the pistons is not affected by the movement of the pistons and will flow through the inlet ports between the chambers and the reservoir without restriction.

The pressurized fluid enters the HCU, which is mounted on the front side of the ABS module. The HCU then modulates the hydraulic pressure to the brakes under the control of the ABS module. For more information, refer to the chapter: Anti-Lock Control - Stability Assist (206-09 Anti-Lock Control - Stability Assist, Description and Function).

(The material was taken from a website: LRMAN.ru)