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Diagnosing Steering System Issues - Not Always the Pump

Power steering diagram

We often assume that problems in the steering system are the power steering pump. It’s an easy and often likely suspect, but it’s not always the cause. Knowing how your vehicle’s power steering system works will help explain what to look for when things aren’t working correctly.

Most modern cars use rack-and-pinion steering with either hydraulic- or electric-assist steering. The term “power steering” can refer to either type of assistance, but a power steering pump is only found on a hydraulic-assist system. These use engine power, through a belt, to turn a pump which pressurizes power steering fluid in the hydraulic system. That pressure is released to add energy to the turn of the wheels. In an electric-assist system, an electric motor powered by the vehicle’s electrical system adds the steering assistance.

The power steering pump is usually located on the front of the vehicle’s engine alongside other accessories such as the alternator and air conditioning pump. An electric-assist system will have no accessories for it on the engine, but will have a motor attached to the steering shaft, usually right above the rack.

When steering assistance becomes erratic, when noises are heard when turning one way or the other, or when steering locks up unexpectedly, there is an issue with the power steering system. Sometimes the problem is as simple as debris getting into the steering rack. Sometimes it could be a broken gear or tooth. The problem could also be in the parts which hold the wheels in place and allow them to turn when the rack moves.

Most of the time, the problem will be the power steering pump. Check its belt tension to be sure it’s not too tight or too loose. Does the belt require replacement? If it’s worn or cracked, it needs to be replaced. If the belt makes a tell-tale whining or “singing” sound, it definitely needs attention. Is the power steering pump’s pulley straight? Observe it as the engine runs to look for wobbles. How about the power steering fluid?

Often overlooked, the power steering fluid in a hydraulic-assist system may need replacement. It should be a closed-loop system which is contaminant free, but the fluid itself can break down over time if left for long periods or overheated. Open the p/s fluid reservoir and remove some fluid using a turkey baster or large syringe. Compare that fluid to new fluid purchased from the auto parts store. Does it look about the same? If your fluid is darker or discolored, it should be replaced. Regardless, whatever was removed should be replaced before going on to the next check.

If your p/s fluid levels are low, check the lines to and from the pump to the rack for leaks. Any wetness that is viscous fluid is probably a leak. This indicates a line that requires replacement. If one line requires replacing, it’s best to do them both.

Next up, check the steering rack. This is difficult without removing the parts themselves. If possible, pull the gearbox that connects the steering rod to the rack and check the gears. Make sure to mark it properly for easy re-installation per your vehicle’s shop manual. Some vehicles have separate covers for the top and bottom of the steering rack which allow you to look at the teeth of the receivers without removing the rack itself. If yours is like this, check those for damage.

Using these tips, you can likely find whatever the problem is with your power steering. There are more, complex tests that can be done as well, but these initial checks should be first on your diagnosis list.