The Power Steering System & Steering Gear

Your vehicle's power steering system comprises several components that facilitate easier and more accurate steering. In the past, cars featured large steering wheels and required significant physical effort to manage the manual steering system. Thanks to advancements in technology, modern vehicles offer much smoother steering experiences.

Key components of the power steering system, located between the steering wheel and steering gear, include the steering wheel itself, steering column, steering coupler, steering gear, power steering hoses, and power steering pump. Traditionally, power steering systems have been hydraulic, but electric power steering systems are becoming increasingly prevalent. Electric power steering systems incorporate additional components such as various sensors, wires, actuators, motors, and an electronic control unit.

There are three basic types of power steering systems found in vehicles: the hydraulic power steering (HPS), the electric power hydraulic steering (EPHS), and the fully electric power steering (EPS). Electric and electronic power steering both refer to the same system.

Hydraulic power steering (HPS) operates by utilizing hydraulic pressure, generated by an engine-driven pump called the power steering pump, to aid in turning the steering wheel. The power steering pump is driven by the accessory drive or serpentine belt, supplying pressurized power steering fluid to the high side power steering hose. This hose then delivers the fluid to the input side of the power steering control valve at the steering gear. Power steering fluid is sourced from the power steering fluid reservoir, which is maintained at the appropriate level by a low side power steering hose. This hose returns the fluid from the gear at a much lower pressure.

Hydraulic power steering (HPS) comes with several drawbacks. Since the power-steering pump found in most vehicles operates continuously and pumps fluid constantly, it leads to horsepower wastage. This wasted power results in fuel inefficiency and higher emissions. Moreover, HPS systems are prone to leaks and noises, often leading to failure caused by a broken belt.

Electric power hydraulic steering (EPHS) represents a hybrid approach combining hydraulic and electric elements. In this system, an electric motor powers the hydraulic pump instead of relying on a belt driven by the engine. In EPHS, the traditional drive belts and pulleys that operate a power steering pump are replaced by a brushless motor. This electric motor drives the power steering, thereby reducing the engine's power consumption.

In the electric power steering (EPS) system, the hydraulic pump is replaced by an electric motor, establishing a fully electric power steering setup. This electric motor is either attached to the steering rack or the steering column, with the steering dynamics controlled by the electronic control unit. EPS is often preferred due to its superior fuel economy and reduced emissions.

EPS offers numerous additional advantages. The level of assistance provided by EPS can be easily adjusted to suit the vehicle type, road speed, and even driver preference. Another benefit is the elimination of environmental hazards associated with hydraulic power steering fluid leakage and disposal. Furthermore, electrical assistance remains operational even if the engine fails or stalls, whereas hydraulic assistance ceases when the engine stops.

The rack and pinion steering gear mechanism converts the driver's steering input into the movement of the front wheels for turning. In this setup, a pinion gear is linked to the steering shaft, so when the steering wheel is turned, it rotates the pinion gear in a circular motion. This motion then translates into linear movement of the rack. Essentially, it converts the rotational motion of the steering wheel into the linear motion necessary for wheel turning. Rubberized plastic bellows are positioned at each end of the steering rack to secure it to the rack body and prevent dust and debris from entering the rack and pinion unit.

On the other hand, the recirculating ball steering gear system also translates the driver's steering input into wheel movement for turning. In this system, a box is mounted over a worm drive containing numerous ball bearings. These ball bearings circulate around the worm drive and move into a recirculation channel before returning to the worm drive. When the steering wheel is turned, the worm drive rotates, causing the balls to press against the channel inside the nut. This pressure forces the nut to move along the worm drive, rotating a Pitman arm, moving the steering linkage, and ultimately turning the wheels.

The steering column serves as the housing that securely holds the steering wheel and shaft in place. Positioned at the bottom of the steering shaft is the steering coupler, a joint that allows the steering wheel to rotate smoothly without binding in the column. This is necessary because the input shaft and steering column are not perfectly aligned and are at a slight angle to each other. The steering coupler connects the steering wheel and shaft to the steering gear.

In vehicles equipped with hydraulic power steering, there are two primary power steering hoses: the high side (high pressure) hose and the low side (low pressure) hose. Both hoses are connected to the rack and pinion using threaded brass fittings. The high side hose is attached to the power steering pump with a threaded brass fitting, while the low side hose slides over a small pipe and is secured with a hose clamp. The high side hose carries pressurized power steering fluid to the steering gear to provide power assistance to steering inputs, while the low side hose carries low-pressure fluid back to the pump and reservoir.

Due to the complexity and interconnection of the power steering and steering gear systems, a comprehensive inspection of these components is essential. Hydraulic elements such as the power steering pump and hoses should be thoroughly checked for any signs of leakage. Additionally, the power steering belt requires examination for damage, cracking, wear, and proper tension. The steering gear warrants inspection for both looseness and leaks, while the bellows boots on rack and pinion steering gear should be scrutinized for tears or damage. It's crucial to ensure the steering wheel and column are securely fastened, and the steering coupler should be securely tightened while still allowing free movement without any noises. For vehicles equipped with electronic power steering, all components should be visually inspected for any signs of damage.

The power steering should be operated both left and right while driving to inspect for binding, noises, and ease of operation. The power steering system and steering gear greatly contribute to the safe operation of your vehicle.