Brakes Released
WARNING: This page does not describe the selected car, but rather 35 other vehicles, including the 1999 GMC Yukon, 1999 GMC Suburban, 1999 GMC Sierra, 1999 GMC Savana Special, and 1999 GMC Savana Camper Special. However, it is still accessible from the selected car via links, so may be relevant.
With brake pedal released, spool valve return spring holds spool valve open. Spool valve allows fluid flow between power steering pump and power steering gear.
Fluid pressure is blocked from entering boost chamber by lands on spool valve. Boost chamber is vented through spool valve, to pump return port, and back to power steering pump.