Power Steering Problems

How to diagnose and repair power steering problems
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Thankfully, power steering is the rule rather than the exception. Thirty years ago, it wasn’t uncommon to drive a car without it. Manual steering was standard equipment in most passenger cars and light trucks and power steering was available as an extra-cost option. With the convenience of power steering is the need to maintain it and troubleshoot power steering problems.

Essentially, the typical (and most common) power steering system is based upon two primary components: The steering box and a hydraulic pump. The hydraulic power steering pump is driven by a belt that may also drive the air conditioning compressor pump and other engine accessories. Typically, a power steering pump will deliver between 650 and 1,300 pounds pressure, depending upon the pump configuration. The fluid used is a special solution developed specifically for this application. In some cases, however, Type "A" automatic transmission is employed.

When it comes to power steering fluid, check the owner's manual or look for a servicing tag on the power steering reservoir before adding fluid. New fluid should always be of the type recommended by the vehicle manufacturer. There's one caveat to the above: A small number of power steering systems are actually electrically assisted, and beyond the parameters of this article.

A large portion of the power steering pump assembly is taken up by a reservoir, which obviously contains fluid for the system. In many cases, the reservoir will incorporate an internal filter screen designed to remove unwanted particles and foreign matter from entering the fluid before it goes to the steering box.

A pair of hoses carries the fluid to and from the pump and the steering box. The smaller of the two hoses is the high-pressure hose, while the larger hose is the return line for the fluid coming back to the reservoir. In most systems, once the fluid circulation reaches a pre-set limit (for example: 2 gallons per minute), the flow control valve opens. This forms a passageway between the inlet and outlet sides of the pump, which allows excess oil to recirculate through the pump (without raising the pressure in the rest of the system).

Suspension and Steering Mechanics

So far so good, but before you begin any power steering system troubleshooting, ensure that any steering or handling problems are not the fault of a mechanical component in the front suspension or steering mechanism. Once you get that portion of the check out of the way, you can turn your attention to the power steering system.

Fluid

When diagnosing faults in the power steering system, first take the time to check the power steering fluid reservoir. Wipe the cover prior to opening to prevent dirt from entering the reservoir. The majority of power steering pumps have a small dipstick built into the reservoir cap. The dipstick will show you the exact fluid level in the reservoir. If there is no specific filling level indicated on the pump or if the dipstick isn't legible, check the shop manual for instructions. If none exist, figure on maintaining the level approximately one inch below the top of the filler opening.

If the fluid level proves to be very low, examine the system carefully for leaks. Check all connections, hoses and couplers for evidence of fluid leaks. Keep in mind that dirt will be attracted to the oil. It may prove necessary to pressure wash the area of the power steering pump and power steering box before you can search for fresh oil leaks. When examining hoses, watch for fraying or cuts. If no leaks are present, the next step is to check the tension of the power steering pump drive belt.

Drive Belt and Belt Tension

The drive belt can also be the cause of power steering trouble. When it comes to v-belts, check the belt for worn or frayed material or glazing of the sides of the belt. Glazing typically indicates the belt is slipping within the drive pulley. Belt tension should be maintained at the factory specifications. Set the belt tension just tight enough (approximately 1/2-inch deflection) so that the belt doesn't slip when the steering wheel is turned completely from side to side with the engine running.

In the case of later model cars and light trucks, a serpentine drive belt is used to "power" accessories. This is a single ribbed belt that drives all of the vehicle accessory systems from the A-C unit to the water pump to the power steering pump. Unlike the v-belt, it doesn't require periodic adjustment (an automatic tensioner is built into the system). But because it's a set-and-forget arrangement, most folks tend to ignore the overall condition of the belt.

Should the serpentine belt become oil soaked or glazed, it is no different than a regular v-belt. It will slip and, as a result, driven accessories (including the power steering) won't function as per normal. When inspecting the belt, look for abrasions or tears on the edges. This could mean the belt is rubbing on a pulley flange, perhaps a bolt, or other fastener. This tends to happen as the belts age. If you discover cracks within the grooves of the belt, keep this in mind: If the cracks are approximately 1/8-inch apart, all around the belt, the belt should be replaced. Typically, a belt will begin to show evidence of cracking (small, short cracks) half way or so into the service life.

Pressure Valves

Finally, it is also possible to check the operation of the power steering pump pressure valves by turning the steering wheel full left and full right with the engine running. During this test, it's important to have proper tire inflation pressures. First, check and set the front tire pressure to recommended values. If these power steering valves are working normally, you should be able to hear a slight buzz as the wheels approach full deflection to one side. If no noise can be heard during the test, a sticking or otherwise malfunctioning valve should be suspected. Do not hold the steering wheel in the extreme right or left position for more than a few seconds. If either of the relief valves is not working, the high pressures built up may damage the system. Repair is beyond the scope of most folks as well as this article. It's best to have the power steering repaired by a mechanic.

For more insight into diagnosing the health of your power steering system and troubleshooting power steering problems, check out the accompanying photos and captions.

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