GM Service Manual Online
For 1990-2009 cars only

The hydraulic power steering system consists of the following components:

    • The pump
    • The fluid reservoir
    • The steering gear
    • The pressure hose
    • The return hose

For bench repair of the integral power steering gear and the hydraulic pump, refer to the following information:

    • Power Steering Gear Unit Repair
    • Power Steering Pump Unit Repair

The power steering pump is a vane-type pump. The pump houses the internal components inside the reservoir. The pump operates submerged in oil.

Two bore openings are located at the rear of the pump housing. The larger opening contains the following components:

    • The cam ring
    • The pressure plate
    • The thrust plate
    • The rotor and vane assembly
    • The end plate

The smaller opening contains the following components:

    • The pressure hose union
    • The flow control valve
    • The spring

The flow control orifice is part of the pressure control union. The pressure relief valve inside the flow control valve limits the pump pressure.

The power steering gear has a recirculating ball system. The system acts as a rolling thread between the worm shaft and the rack position. The lower end of the worm shaft is supported by a preloaded thrust bearing and two conical thrust races. The upper end of the worm shaft is supported by an adjusted plug. When you turn the worm shaft right, the rack piston moves up in the gear. When you turn the worm shaft left, the rack piston moves down in gear. The rack piston teeth mesh with the sector. The sector is part of the pitman shaft. The pitman shaft turns the wheels through the steering linkage.

The control valve in the steering gear directs the power steering fluid to either side of the rack piston. The rack piston converts the hydraulic pressure into a mechanical force. You can control the vehicle manually if the steering system becomes damaged and loses hydraulic pressure.