Symptoms of a Failing Power Steering Box

Written by edmund gary
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Symptoms of a Failing Power Steering Box
(Image by, courtesy of Sudhamshu Hebbar)

The power steering system allows the driver to apply steering input on the steering wheel, and an engine-driven hydraulic pump transfers the torque to the wheels. Forces of inertia, weight and friction are overtaken with minimum effort.

Normal Operation

The power steering pump is driven by the engine via a pulley and drive belt. The pulley turns the pump rotor. A series of vanes fit between the pump housing and the rotor. Fluid flows at low pressure from the reservoir into the pump housing. The fluid is picked up by the rotating vanes and forced into a constricted spot. The fluid pressure rises to the required level. The increased pressurised fluid is forced out of the pump into a pressure hose that leads into the steering gearbox or rack. If too much pressure builds up, a relief valve opens to allow the pressurised fluid to return to the reservoir.

Power Steering Fluid Condition

The fluid's appearance reveals a lot about the condition of the power steering pump and system. Fresh power steering fluid is dyed red and has a distinctive odour. Dark grey fluid indicates oxidation in the system. Foaming or bubbles in the fluid indicates air or water in the system. Pump degradation is characterised by chrome plating flowing through the system.


Fluid levels must be checked often. Chronically low fluid levels indicate the presence of a leak from the pump or other system components. Leaks are one of the most noticeable symptoms of power steering pump failure, which present themselves when the vehicle is parked. Fittings and hoses leading to the steering gear must also be checked when there is evidence of a leak. Low fluid levels can cause the power steering pump to operate noisily.

Drive Belts

Improper belt tension can cause power steering pump failure if left unchecked. Worn or broken belts can slip and will not turn the pulley efficiently. Overheated belts can transfer their heat to the pulley and shaft system of the power steering pump. Difficulty steering is another symptom that indicates loose drive belts. Belts should be checked for cracks, missing chunks and/or improper tension at least once a month. The wear indicator on belts are harder to detect. Change the belts after four years of service.

Pump Noises

A constantly noisy pump is a sign of trouble brewing in the power steering pump or system. A buzzing noise when the wheel is straight can be attributed to a noisy pump, damaged hydraulic lines, pressure control valve sticking, air in the system or a failing pump. A clatter indicates the cushion for the back pressure valve is either missing or broken.

Steering Characteristics

The ease of steering can also be an indication of the health of the pump. Hard steering and/or temporary increases in effort when turning the steering wheel can be caused by low oil level. This may be accompanied by noise from the pump. An oily, loose pump belt or a faulty power steering pump may also be the cause of hard steering.


Car owners need to use their eyes and ears to detect whether the power steering pump is about to fail. Identifying the signs of failure early can aid in getting a repair quickly.

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