ps

Power steering, abbreviated ps, is a hydraulic or electric system that reduces the physical effort needed to turn a vehicle's steering wheel. A pump driven by the engine (or an electric motor) pressurizes fluid that acts on a control valve linked to the steering column. When you turn the wheel, the valve directs pressurized fluid to one side of a piston in the steering gear, multiplying your input force and easing the turn. Without it, steering a heavy vehicle at low speeds or while parked demands substantially more effort from the driver.

Hydraulic power steering has been the standard since the 1950s. The system includes a pump, pressure hose, control valve, piston assembly, and return line; fluid circulates continuously, with excess pressure relieved by a safety valve. Electric power steering, introduced in passenger cars from the early 2000s onward, uses an electric motor mounted directly on or near the steering gear to assist rotation, consuming power only when the wheel is being turned. This design improves fuel economy and allows integration with electronic stability and lane-keeping systems.

The control valve is the critical component in hydraulic systems. As the driver turns the wheel, the valve spool shifts, directing pressurized fluid to the appropriate side of the piston. The amount of assistance varies with steering angle and, in modern systems, vehicle speed. At highway speeds, power steering reduces assist to maintain road feel and stability; at parking speeds, maximum assist is available. Loss of power steering feel, fluid leaks, whining noises, or a heavy or unresponsive wheel all signal wear or failure in the pump, hose connections, or control valve.

Hydraulic fluid in power steering systems must tolerate sustained pressures of 1000 to 1500 psi (7 to 10 MPa), resist thermal breakdown, and minimize foaming. Mineral oil-based fluids remain common, though some systems use synthetic blends. Electric systems eliminate the need for pump-driven hydraulic circuits, reducing parasitic drag on the engine and simplifying the layout; they are now dominant in new vehicle designs.

Power steering is not optional in modern vehicles. Regulatory requirements for steering effort, combined with heavier vehicles and wider tyres, make unassisted steering impractical for the average driver. The abbreviation ps appears on steering fluid labels, in service manuals, and on specification sheets; technicians distinguish between hydraulic ps and electric ps, or eps, depending on the architecture being serviced.