Almost every modern car is now equipped with some variant of hydraulic power steering, and if it fails, you’ll almost immediately notice your car’s steering get heavier as you struggle to turn the steering wheel.
Regular power steering maintenance is the only sure way to avoid this happening to you.
How Powering Steering Works
Your car’s power steering system is operated by a hydraulic pump connected to a rack and pinion. When you turn your car’s steering wheel, the pinion turns and moves the rack left or right, which then pushes and pulls your tires in the appropriate direction.
As the pinion moves either left or right on the rack, it moves a seal inside of a hydraulic chamber. As the seal moves, it triggers the hydraulic pump, electronically or by a system of pulleys, to either pump more fluid from the left side to the right side of the seal, or vice versa. As the pump pumps hydraulic, it causes a pressure change. The pressure is then exerted on to the outer seal, which moves the tie rods and helps push and pull the wheels in the correct direction.
How Can Power Steering Fail?
When power steering fails, it is because there is not enough pressure being generated in the steering system.
The most common cause of pressure loss is sealing failing. A power steering pump can produce pressure from anywhere between 800 and 2000 pounds. When the pump fails, no pressure can be produced and the power steering will not work at all.
With the high pressure produced by the pump, the rubber seals that keep the hydraulic fluid contained can begin to age and crack, the much-needed power steering fluid begins to be forced out from the edges of the seal. When enough power steering fluid has escaped, the pump can no longer build sufficient pressure.
Another cause of failure is old and dirty power steering fluid. As the fluid ages and collects dirt, the dirt can change the consistency of the power steering fluid. If the fluid becomes too viscous, or not viscous enough, due to dirt or the natural process of the fluids breaking down, it can either fail to generate enough pressure or not be thin enough to pass through the pump.
In extremely dirty power steering fluid, the dirt can clog the pump, hydraulic lines, and even cause the seals to degrade prematurely.
In the most extreme circumstances belts on the pulleys or sensors for electrical systems, can fail, and this causes the pump to either be driven or not receive the appropriate signals. Not all issues with steering are due to power steering as the teeth on your rack and pinion can break and cause a lack of response in the car’s steering, but is a very rare occurrence.
Repair and Maintenance
With all of the fluids in a car, power steering fluid needs to be replaced and is the most frequent form of maintenance you will do on your power steering and can be done during your regular service.
Each manufacturer has their own suggestions on how often power steering fluid should be replaced, and the owner’s manual should be consulted. While the steering fluid is drained from the system, it is common for mechanics to apply a silicon grease, or weathering spray to seals to ensure they last longer.
When the system fails, your mechanic will begin by completely disassembling the steering system so that all hydraulic lines can be cleaned properly. The pump will always be tested and replaced if necessary, and while seals may not need to be replaced, it is good practice to repair them while the system is disassembled as a form of preventative maintenance.