The power steering pump may seem like a magical black box to many, enhancing driving trips and making them enjoyable. However, the exact working mechanism is often questioned. If you’re here to explore beyond the surface, we’ll delve deep into the mechanics, specifically the inner workings of a steering pump.
What is Power Steering Pump?
In a hydraulic power steering system, the steering rack and the steering pump work together, similar to inseparable pairs like Batman and Robin or Thor and Mjolnir. The power steering pump, a centrifugal vane type hydraulic pump, pressurizes steering fluid through high-speed rotations to provide “power assist” for steering.
Simply put, it functions like a water pump but with steering fluid, pressurizing and distributing it to make steering easier. The steering rack enables actual trajectory changes in the car’s tires, while the steering pump makes the steering wheel feel light and easy to turn. You can easily spot the coconut-sized steering pump attached next to your car’s engine by following the engine belt.
Power Steering Pump Working
The power steering pump, often called the “heart” of the system, is just one part among many supporting components. Understanding the entire power steering system can be challenging, especially for newcomers.
It can be divided into three sections:
- Outside the pump
- Inside the pump
- After the pump
Outside the Pump
- The steering fluid reservoir holds the power steering fluid in a yellow-ish container.
- The reservoir supplies the steering fluid to the steering pump through rubber hoses.
- The steering pump is spun using power from the car engine, transmitted through an engine belt connected to the pump’s pulley.
- The crankshaft rotates once you start the engine.
- This causes the steering pump to spin and pressurize the steering fluid.
- The steering pump now starts working
Inside the Pump
- The steering pump pressurizes the steering fluid by using a rotor and vanes.
- The vanes are pushed outward against the pump housing due to centrifugal force, creating tiny chambers that trap the steering fluid.
- The pump housing is oval-shaped, and as the rotor rotates, the steering fluid moves from a larger area to a smaller area, increasing pressure.
- High-pressure steering fluid exits the pump through the pressure control valve, creating a void that draws in more fluid from the reservoir.
- The high-pressure steering fluid then enters the two hydraulic chambers of the steering rack.
Pressure = Force / Area
Pascal’s Law
After the Pump
Sure, here’s the process described in points:
- The high-pressure steering fluid leaves the steering pump and enters the steering rack, which is divided into two hydraulic chambers – left and right.
- The fluid distribution in the hydraulic chambers creates a pressure difference, making one chamber stronger than the other.
- The steering rack pushes either to the left or right, depending on the pressure difference, providing power assist.
- The power assist is the reason why the steering wheel feels lighter when your car has a power steering system.
- The steering fluid exits the steering rack through steering hoses and returns to the steering fluid reservoir.
- The process continues repetitively until the engine is turned off.
Types of Power Steering Pump
Various types of power steering pumps are employed to operate the system. The primary distinction among these pumps lies in the design of the fins responsible for moving and expelling the steering fluid under pressure. Despite the variations, all pumps consist of a spinning rotor within the housing. In total, there are four types of power steering pumps commonly used in steering systems.
Vane Power Steering Pump
The most common type of power steering pump used is the vane pump. In this type of pump, the rotor is housed in an oval- or elliptical-shaped housing, where it is turned. Vanes fitted to the outside diameter of the rotor sit against the housing walls as the rotor turns. When power steering fluid enters the vane pump housing, it becomes trapped between the vanes, the housing wall, and the rotor. Subsequently, the fluid is pumped out of the housing and through the outlet chambers due to the increase in pressure.
Roller Power Steering Pump
The roller power steering pump uses steel rollers in wide V-shaped grooves on the rotor to trap fluid. Centrifugal force pushes the rollers to the oval’s outer edge, creating pressure and forcing the pressurized fluid out through two outlets to drive the power steering system.
Slipper Power Steering Pump
Similar to the vane and roller pumps, the slipper power steering pump (figure 5) also consists of a rotor housed in an elliptical-shaped chamber that rotates within the pump body. Springs with scrubber-type “slippers” are fitted into wide slots on the rotor, ensuring constant contact with the pump’s wall. When fluid enters the pump, pressure builds up and is released to drive the power steering system.
Gear Power Steering Pump
In the gear power steering pump, a void and suction are created on the intake side of the pump as the gears rotate, and fluid is drawn into it. The fluid is then carried by the gears to the discharge side of the pump, where it is displaced by their meshing.
How to replace a Power Steering Pump?
Tools needed to replace a Power Steering Pump
To replace a power steering pump, you will require some or all of the following tools:
- New power steering pump
- Power steering fluid
- Socket wrench set and different sockets
- Set of wrenches
- Power steering pulley remover and installer kit
- Tool for removing power steering hoses
- Container for draining fluid
- Car jack and jack stands or car ramps
- Torque wrench
Steps to replace a Power Steering Pump
Drain the Power Steering Fluid
The power steering system, which contains hydraulic fluid, needs to be drained. Locate a low spot on the system, usually a power steering cooler line, and disconnect it to drain the fluid into a drain pan. Safely dispose of the fluid.
Remove the old Power Steering Pump
To remove the power steering pump, release belt tension, disconnect hoses, and remove securing bolts. The old pump should be free for removal.
Transfer the Pump Pulley
If your new power steering pump doesn’t come equipped with a pulley, the pulley will need to be transferred from the old one. This can be done using a power steering pulley remover and installer kit.
Install the New Power Steering Pump
Install the new pump in reverse order of removal. First, attach hard-to-reach hoses. Then, mount the pump in the same orientation as the old one, tighten bolts as per manual, and complete remaining connections. Finally, install the drive belt.
Refill the Power Steering Fluid
To add fluid, use a sealed container of compatible power steering fluid. Purge air by turning the wheel left and right with the engine off. Start the engine, turn the wheel again, and check for smooth operation. To make sure everything works perfectly you cant take a test drive.
Video on Power Steering Pump
FAQ’s
→Drain power steering fluid.
→Release belt tension and remove belt.
→Remove old pump, disconnect hoses.
→Transfer pulley (if needed).
→Install new pump, connect hoses, add fluid, purge air, and test drive.
→Listen for noises: Whining (pump) or clunking (rack).
→Check for fluid leaks.
→Difficulty steering.
→Steering wheel vibration.
→Uneven tire wear.
The cost of a power steering pump can vary. It comes in between $100 to $500, It depends on the specific make and model of your vehicle.
