X-90 (4WD) L4-1591cc 16L SOHC MFI (1998) Steering and Suspension Power Steering Pump Diagrams
The steel ball in the relief valve is under the hydraulic pressure in the circuit coming through orifice A2. When the steering wheel is turned and the
hydraulic pressure increases higher than 70 kg/cm2 (1000 psi), it compresses the relief spring to push the steel ball which then allows the fluid to
flow to the P/S pump.
Such relief valve operation causes a pressure difference to occur between chambers A and B.
Then the flow control valve moves to the right to make opening in orifice A1 narrower, maintaining the hydraulic pressure constant.