Essential Power Steering Parts and What they do

January 27, 2012

On newer cars, with rack and pinion steering, there are two main power steering parts, the pump, the rack and pinion unit and hoses. Listed below are all of the components in a modern power steering system, and the functions they serve.

General System Function

In a modern power steering system, the pump provides power steering fluid under pressure to the rack and pinion unit. When the driver provides steering input by turning the steering wheel, the power steering control valve applies fluid pressure to one side of a piston, which assists the driver in turning the wheel. When the wheel is turned, the pinion turns against the rack, and both being gears, this pushes the rack in the desired direction, which turns the wheels.

Power Steering Pump

The power steering pump is turned by the accessory drive belt or serpentine belt to develop fluid pressure in the high side power steering hose to the input side of the power steering control valve.

Rack and Pinion

The rack and pinion is the unit which translates driver steering input into movement of the front wheels for turning. Attached to the end of the steering input shaft is a pinion gear. This gear is pressed against the steering rack. As the steering wheel is turned, the pinion rotates and pushes the rack in the direction desired. On either end of the steering rack are rubberized plastic bellows, which secure to the rack body and the moving part of the rack to keep dust from entering the rack and pinion unit.

Steering Yoke

Between the rack and pinion input shaft and the steering column is the steering damper. This is a thick rubber piece which absorbs road shocks and prevents them from being transferred to the driver through the steering wheel.

Steering Coupler

This is a joint that allows the steering wheel to rotate without binding up in the column, due to the fact that the input shaft and steering column are not in perfect alignment, but at a slight angle to each other.

Tie Rod Ends

These are components that attach the ends of the steering rack to the steering knuckle and allow the motion of the rack to be translated into turning movement of the front wheels. These parts rotate horizontally for steering input translation and pivot vertically as well as diagonally, when the vehicle encounters roughness in the road and the wheels bounce.

Power Steering Hoses

There are two main power steering hoses, the high side and the low side. Both are attached to the rack and pinion with threaded brass fittings. The high side hose is attached to the power steering pump with a threaded brass fitting, while the low side hose slides over a small pipe and is secured with a hose clamp. The high side hose carries power steering fluid under pressure to the rack to provide the power assist to steering inputs. The low side hose carries low pressure fluid back to the pump.

After reading the preceding information, you should now have a better understanding of the components and function of the power steering system on your car.

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