Braking Position

As brake pedal is depressed, it moves pedal rod and spool valve. This closes fluid return to pump, and admits fluid into boost chamber from pressure port. Additional valve movement restricts flow between pump and steering gear.

As fluid pressure increases in boost chamber, it forces piston forward, actuating master cylinder piston and applying brakes. If fluid pressure is required for steering while braking, pump pressure will rise and spool valve will shift in an open direction allowing more fluid to flow to steering gear.