The components that are common to all power steering systems are as follows:

in the system. There are four basic types of power steering pumps- vane, roller, slipper, and gear types. A belt running from the engine crankshaft pulley normally powers the pump. During pump operation, the drive belt turns the pump shaft and pumping elements. Oil is pulled into one side of the pump by vacuum. The oil is then trapped and squeezed into a smaller area inside the pump. This action pressurizes the oil at the output, as it flows to the rest of the system. A pressure relief/ flow valve is built into the pump to control maximum oil pressure. This action prevents system damage by limiting pressure developed throughout the different engine speeds.

POWER STEERING PUMP (fig. 8-25)- The power steering pump is engine-driven and supplies hydraulic fluid under pressure to the other components

CONTROL VALVE (fig. 8-26)- The controlvalve (rotary or spool type), which is actuated bysteering wheel movements, is designed to direct the

Figure 8-25.- Typical power steering pump.

Figure 8-26.- Control valve.

hydraulic fluid under pressure to the proper location in the steering system. The control valve may be mounted either in the steering mechanism or on the steering linkage. depending on which system configuration is used.

POWER STEERING HOSES- Power steering hoses are high-pressure. hydraulic rubber hoses that connect the power steering pump and the integral gearbox or power cylinder. One line serves as a supply line, the other acts as a return line to the reservoir of the power steering pump.

There are three major types of power steering systems used on modern passenger vehicles (fig. 8-27)- integral piston (linkage type), external cylinder (linkage type), and rack and pinion. The rack and pinion can further be divided into integral and external power piston. The integral rack and pinion steering system is the most common.