What is Power Steering? 

Turning a two- or three-ton vehicle without any assistance would be an extremely challenging task, especially overcoming friction with the ground at a stop. But in the early fifties, power steering systems have been installed – first as an option and then, in the past few decades, as standard equipment. It’s often taken for granted or not fully understood, despite its importance in convenient and safe driving.

Several key components make up the power steering system among two different designs. Here’s what you need to know about power steering system operation, the parts involved, and what can go wrong.

Types of power steering 

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When there’s no steering assist system, it’s called manual steering. In today’s market, there are almost no mass-produced vehicles sold without power steering installed.  There are two common designs used today: hydraulic power steering assist and electric power steering assist. 

Both types of systems are intended to reduce the amount of effort required to turn the wheels at the steering wheel. It takes the driver’s input and amplifies it to maneuver the vehicle with less effort. It’s particularly helpful at low speeds and with heavy vehicles where the friction to overcome at the steering wheels would otherwise require strenuous energy. 

Hydraulic power steering 

In a hydraulic power steering system design, fluid power is employed to reduce the amount of strength needed for steering input. A power steering pump driven by the serpentine belt or power steering belt is constantly turning while the engine is running, pressurizing the system. When the driver turns the steering wheel left or right, pressurized fluid travels through a hose to the steering rack. A spool valve at the rack determines if it’s directed to the left or right side based on the direction the steering column moves.  

The fluid pressure inside the steering rack reduces the energy required by the driver’s steering input, using a hydraulic piston inside to move the tie rods side to side. This, in turn, makes the wheels move. 

Hydraulic power steering is still relatively common since it’s familiar and comparatively inexpensive to repair, but it isn’t ideal since there’s wasted energy. No matter what, when the engine is running, the power steering pump is rotating. As well, any leaks or failures cause the loss of power steering. 

Electric power steering  

Electric power steering, or EPS, replaces the fluid-powered components with those that draw from the car’s electrical system instead. Torque sensors on the steering shaft detect the steering wheel position and the driver’s input, and an electric motor springs into action to move the rack and pinion side to side.  

For EPS, there are two major designs employed. One has an electric motor mounted at the steering rack, which tends to be used for the luxury and high-performance market. The other is a more common steering column-mounted electric motor. They operate either on 12 volts like other car electronics or on 48 volts. 

Common problems with power steering 

Neither the hydraulic nor electric power steering system is foolproof, and problems can happen with either one.  

HPS issues 

For hydraulic systems, the weak spot in the steering system tends to be focused around the fluid itself. Common points of failure can include:  

  • Blown power steering hoses. In cold weather especially, the power steering pressure hose can rupture and leak large amounts of fluid quickly. 
  • Power steering pump problems. Since the pump is constantly turning when the engine is running, the pump can wear out or develop leaks from seals. It can also become noisy. 
  • Power steering rack and pinion. A range of issues can develop in the rack and pinion including leaks at the bellows boot seals, bent inner tie rods, or wear or play in the work gear or pinion gear. 
  • Fluid problems. Using the wrong fluid in the system can contaminate and damage seals and hoses, and lack of fluid maintenance can lead to worn parts from improper lubrication. 

EPS issues 

Although there are fewer moving parts involved, there can still be problems with an electric power steering system.  

  • The electric steering motor can fail. If the motor has an internal fault, it can stop working altogether or trigger a fault code in the computerized control that disables electric power steering and triggers a warning light. 
  • The torque sensor can fail. This sensor determines how much assistance is provided by the electric motor. If it isn’t reading correctly, it can also disable the EPS. 
  • Vehicle speed sensor. Since the EPS has variable assist based on vehicle speed, a speed sensor fault can disable the EPS. 
  • Steering gear faults. Wear inside the rack and pinion can cause noises or looseness that needs to be addressed. 

What does it cost to fix the power steering? 

The problems that can pop up in a power steering system can range from a small issue that’s an inexpensive fix to a repair that’s well over $1,000. For example, a broken power steering belt can often be replaced for $20 or less, and a power steering pump can range from under $100 to more than $800. A hydraulic power steering rack is more likely to range from $200 to over $2,000, depending on what you drive.  

For the electric power steering system, the assist motor can range from $60 to more than $1,000. The related sensors have a similarly wide range, and an electric power steering rack is also a costly item.  

Shop at AutoZone for your power steering parts or to get Trustworthy Advice on keeping your vehicle in tiptop shape. If you decide that it’s too big a job to tackle on your own, let AutoZone help you find qualified professional mechanics through our Shop Referral Program.  

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