Brakes Applied
WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1992 GMC Yukon, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Value Van, and 1992 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.
Pressing pedal 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 power steering pump and power steering gear.
As fluid pressure increases in boost chamber, it forces piston forward, actuating master cylinder piston and applying brakes. If steering is required while braking, power steering pump pressure will rise and spool valve will shift open, allowing more fluid to flow to power steering gear.