What Power Steering Consists Of: The Parts Behind Lighter, Safer Steering

Power steering consists of a mechanical steering gear connected to the wheels plus an assist system—either hydraulic (fluid and pump) or electric (motor and control unit)—that reduces the driver’s effort. In practice, that means a steering wheel and column, a steering gear (rack-and-pinion or recirculating ball), and either hydraulic components (pump, reservoir, hoses, valve, and assist piston) or electric components (motor, reduction gear, sensors, and ECU), with safety and control electronics layered on top. Here’s how those pieces fit together in modern vehicles.

The Core Mechanical Path (What Every System Shares)

Regardless of how the assist is generated, every power steering system retains a mechanical path from the steering wheel to the road wheels for control and safety. These parts transmit driver input and, in most designs, provide a fail-safe connection if assistance is lost.

• Steering wheel and steering column
• Universal joints and intermediate shaft
• Steering gear: rack-and-pinion (most cars/crossovers) or recirculating ball (many trucks/heavy-duty)
• Tie rods (inner and outer) and steering knuckles
• Column lock mechanism (anti-theft) and collapsible column sections (safety)

Together, these components translate rotation of the steering wheel into turning motion at the road wheels; the assist system simply adds or subtracts torque along this path.

Hydraulic Power Steering (HPS): Traditional Fluid-Based Assist

Conventional hydraulic power steering uses pressurized fluid from an engine-driven pump to assist the driver. It’s common on older vehicles and many heavy-duty applications.

• Engine-driven hydraulic pump (typically a vane or roller pump), driven by a belt
• Drive belt and pulley(s) for the pump
• Fluid reservoir (often with an integrated filter or screen)
• Hydraulic fluid (PSF or specified ATF, depending on vehicle)
• High-pressure hose/line and low-pressure return hose
• Rotary spool/control valve integrated in the steering gear
• Assist piston or power cylinder (built into the rack housing or external on recirculating-ball gears)
• Pressure relief valve and, in some designs, a fluid cooler
• Seals, O-rings, and fittings throughout the system

When the wheel is turned, the control valve routes pressurized fluid to one side of the assist piston, adding force to move the rack or sector shaft; the relief valve limits peak pressure, and fluid returns to the reservoir via the low-pressure line.

Electro-Hydraulic Power Steering (EHPS): Electric Pump, Hydraulic Assist

EHPS replaces the engine-driven pump with an electric motor-driven pump, improving efficiency while retaining hydraulic assist. It was a common bridge technology in the 2000s–2010s and still appears on some vehicles with higher steering loads.

• Electric hydraulic pump module (motor, pump, and often the reservoir in one unit)
• Power and ground wiring, relay(s), and appropriate fusing
• Control module (sometimes integrated into the pump unit)
• Hydraulic lines (high- and low-pressure), reservoir, fluid, and control valve in the steering gear
• Inputs such as vehicle speed or steering torque for variable assist

The electric pump builds pressure on demand, reducing parasitic losses versus a belt-driven pump; the hydraulic steering gear and valve operate similarly to HPS.

Electric Power Steering (EPS): Motor-Driven Assist With Electronics

EPS replaces hydraulic pressure with an electric motor that adds torque to the steering shaft or directly to the rack. Most new passenger vehicles now use EPS because it’s efficient, tunable, and integrates easily with driver-assistance features.

Column-Assist EPS (Motor on the Steering Column)

In column-assist systems, the motor and reduction gear sit on the steering column inside the cabin, adding torque directly to the column shaft.

• Electric motor (often brushless) mounted to the steering column
• Reduction gearset (worm or belt/gear drive) and sometimes a clutch
• Torque and angle sensors on the column to measure driver input
• EPS control unit (ECU) with power electronics (inverter) and thermal management
• Power supply wiring, fuses, and sometimes a backup power path
• Diagnostic interface and warning indicator (dashboard light)

The ECU compares driver torque to vehicle conditions and commands the motor to add assistance proportionally; column EPS is compact and common in small-to-midsize vehicles.

Rack-Assist EPS (Motor on the Steering Rack)

Rack-assist systems mount the motor on or within the steering rack, applying assist closer to the road wheels for higher capacity and precision.

• Brushless motor integrated with the steering rack housing
• Ball-screw or belt drive that translates motor torque into rack force
• Integrated control module with sensors and power electronics
• Steering angle and rack-position sensing for accurate control
• Enhanced thermal management for sustained assist and towing loads

By acting directly on the rack, these systems deliver stronger, more consistent assist—favored in midsize to large vehicles and performance applications.

Control, Sensing, and Safety Features (Modern Systems)

Beyond basic assist, contemporary power steering includes electronic sensing and safety logic, especially in EPS, to tailor feel, support driver-assistance, and provide fail-safes.

• Steering torque and angle sensors to interpret driver intent
• Vehicle speed input for variable assist and on-center stability
• Yaw rate and lateral acceleration data for stability control integration
• ECU algorithms for damping, return-to-center, and road feel calibration
• Redundancy and limp-home modes to maintain steerability upon faults
• Torque overlay capability for ADAS features (lane keeping, lane centering, park assist)
• Diagnostic trouble codes (DTCs) and warning indicators for service

These layers make steering lighter at low speeds, firmer at highway pace, and compatible with driver-assistance features while preserving a controllable backup if assist is lost.

Maintenance and Typical Failure Points

What fails depends on the type of system. Hydraulic systems consume fluid and use belts and hoses; EPS relies on sensors, wiring, and motor control electronics.

• HPS/EHPS: fluid leaks (hoses, seals), contaminated fluid, noisy or weak pump, slipping or worn belt, sticky spool valve, and degraded bushings
• EPS: torque/angle sensor faults, motor overheating, worn reduction gears, corroded connectors or grounds, low voltage supply issues
• Common to all: worn tie rods, alignment drift, and play in the steering gear affecting feel and precision

Regular checks—fluid condition (if hydraulic), belt condition, alignment, and prompt attention to warning lights or unusual noises—help preserve steering performance and safety.

How to Tell Which System You Have

Identifying the system helps with maintenance and troubleshooting. Visual and operational clues can quickly narrow it down.

• Hydraulic: belt-driven pump on the engine, fluid reservoir and hoses, assist noise that varies with engine speed
• Electro-hydraulic: electric pump unit (often near the fender or subframe), reservoir and hoses but no pump belt
• Electric: no power steering fluid reservoir; a motor on the column under the dash or integrated into the steering rack
• Owner’s manual and under-hood labels often specify the system and fluid (if applicable)

A quick under-hood check for a reservoir and pump typically distinguishes hydraulic types from EPS; the location of the motor separates column- from rack-assist EPS.

Where the Technology Is Headed

Most new passenger vehicles use EPS for efficiency and ADAS integration. Premium and performance models increasingly feature high-capacity rack EPS with refined software tuning. Steer-by-wire systems—where electronics replace the mechanical link—are emerging in limited production with mechanical backups for safety, and 48-volt electrical architectures are expanding assist capacity in large vehicles.

Summary

Power steering consists of a mechanical steering path plus an assist system. Hydraulic systems use a pump, fluid, hoses, control valve, and assist piston; electro-hydraulic swaps the pump for an electric unit; full electric systems use a motor, reduction gear, sensors, and an ECU to deliver variable, efficient assist. No matter the type, the steering wheel, column, gear, and tie rods form the backbone, while sensors and electronics increasingly shape feel, safety, and driver-assistance capability.

Can you still drive a car if the power steering goes out?

Yes, you can still drive a car without power steering, but it will be much harder to steer, especially at low speeds or when parking, requiring significant physical effort. You should get your vehicle serviced as soon as possible to prevent further damage or potential accidents. When the power steering fails while driving, turn on your hazard lights, carefully pull over to the shoulder, and slow down before coming to a stop. 
How to Drive Without Power Steering

• Use Both Hands: Grip the steering wheel firmly with both hands to maintain control. 
• Be Prepared for More Force: You’ll need to use more physical force to turn the wheel, particularly for sharp turns. 
• Increase Engine RPMs: In a hydraulic power steering system, increasing engine speed can help the pump provide more assistance, making steering easier, especially for turns at speed. 
• Be Patient: Take your time to change lanes and make turns, as you won’t be able to counter-steer as quickly as usual. 

Why It’s Dangerous

• Accident Risk: The increased difficulty in steering can lead to loss of control, especially in emergency situations or tight corners. 
• Component Damage: Driving with a failing power steering system can cause further damage to the pump or other components. 
• Sudden Failure: The loss of power steering can be sudden and unexpected, catching drivers off guard. 

What to Do if Power Steering Fails

1. Signal: Turn on your hazard lights to alert other drivers to a problem with your vehicle. 
2. Move to the Shoulder: Carefully and slowly pull your vehicle to the side of the road. 
3. Brake Gradually: Lightly apply the brakes as you pull over and come to a complete stop. 
4. Get it Inspected: Contact a mechanic to diagnose and repair the issue as soon as possible. 

Is it expensive to fix power steering?

Yes, fixing a power steering issue can be expensive, with costs ranging from under $100 for a simple fluid flush to $800 or more for a new power steering pump, and even higher for complex repairs like a steering rack replacement. The final cost depends on the specific problem, your vehicle’s make and model, the parts used (OEM vs. aftermarket), and your location. 
Breakdown of Common Repairs and Costs

• Power Steering Fluid Flush: Opens in new tabIf the issue is dirty fluid, this can resolve the problem for approximately $50 to $150. 
• Power Steering Pump Replacement: Opens in new tabThis is one of the more expensive repairs, with average costs ranging from $500 to $900, though it can go higher for luxury or large vehicles. 
• Power Steering Hose Replacement: Opens in new tabA leaking hose is generally a less expensive repair, potentially costing around $60 to $150, depending on the specific hose and labor involved. 
• Steering Rack Replacement: Opens in new tabThis is a significant and expensive repair, with parts and labor for a steering rack replacement costing several hundred dollars. 

Factors Affecting Cost

• Vehicle Make and Model: Luxury cars and larger vehicles typically have more expensive parts and labor. 
• Part Type: Using an Original Equipment Manufacturer (OEM) part from your car’s manufacturer is usually more expensive than an aftermarket part. 
• Labor Costs: The hourly rate for mechanics varies by location and shop. 
• DIY vs. Professional Repair: If you are comfortable with car maintenance, you can save money by doing some repairs yourself, but it’s important to ensure you have the right tools and knowledge. 
• Additional Repairs: Power steering issues can sometimes lead to other necessary repairs, such as a wheel alignment after a steering rack replacement. 

What does a power steering system consist of?

Power steering systems are either hydraulic (HPS) or electric (EPS), though nearly every vehicle manufacturer is turning to or has already turned to electric power steering. In hydraulic systems, a pump pressurizes fluid to help turn the wheels, while an electric system uses an electric motor to assist.

What is the most common cause of power steering failure?

The most common causes of power steering failure are a power steering fluid leak and issues with the power steering pump itself, with other causes including a loose or slipped drive belt, worn hoses, and, in the case of electric power steering (EPS), a faulty electronic control unit (ECU) or motor. Low or contaminated fluid can starve the pump, causing it to fail, while a leak is often the root cause of low fluid levels. 
Common Problems with Hydraulic Power Steering 

• Leaking Fluid: Opens in new tabLeaks are a frequent problem because high-pressure fluid flows through hoses and connections, which can wear out over time, crack, or develop loose couplings. 
• Low Fluid Levels: Opens in new tabA leak directly leads to low fluid levels, which can then damage the pump as it tries to operate with air instead of fluid. 
• Worn-Out Power Steering Pump: Opens in new tabThe pump’s seals and internal parts can wear out with age and use, leading to a loss of pressure or complete failure. 
• Slipped or Broken Drive Belt: Opens in new tabThe belt that drives the pump can slip off or break, preventing the pump from working. 
• Clogged Hoses or Contaminated Fluid: Opens in new tabDebris, wear from internal components, or even old, dirty fluid can restrict fluid flow, overworking the pump and causing it to fail. 

Common Problems with Electric Power Steering (EPS)

• Electronic Control Unit (ECU) Failure: A malfunction in the ECU can cause the power assist to be lost or intermittent. 
• Malfunctioning Electric Motor: The electric motor that provides the assist can fail, leading to difficult steering. 
• Blown Fuse: A simple blown fuse can cut power to the electric power steering system. 
• Loose or Faulty Connections: Loose wiring or connections to the motor or ECU can cause the system to malfunction.