Have you ever noticed a loud noise when turning the steering wheel, sounding like something is whining under the hood? There are many systems and components that move and spin while the engine is running. Because of this, tracking down the source of the noise can sometimes be hard. However, if the whining noise happens only when turning the wheel, chances are you have an issue with your steering system. In this article, we will explain how the steering system works, which assistance devices it uses and what can go wrong.
How Does a Steering System Work?
Although the steering system may appear simple at first, there is some amazing physics and mechanisms beneath it, which keeps your car on the track with no slipping. When you tilt the front wheels, your car will turn in that direction because of the sideway forces. They happen because of different translational speeds between the tilted wheels and the road below it. The only way for canceling these forces is by making sure the whole car turns around a particular center point.
Although there are other variants, the rack and pinion type are the most commonly used steering mechanisms in modern vehicles. The rack is constrained and the pinion that comes from the steering wheel can only move it in a straight line. A part called a steering arm, on which the wheel is attached, connects to the car frame with strut mount bearing and ball joints. Being constrained like that, it can only rotate around the vertical axis. In the end, a tie rod connects the steering arm to the rack and has both translational and rotational motion.
Another important fact here is that the perpendicular lines from the front wheels should meet the real wheel axis at a common point. Observe closely and you may notice that the angles turned by the left and right wheels are not the same. This means that for perfect steering, the left and right wheels should turn at different angles. To ensure safe turns, the meeting point of the left and right wheels always lies on the rear wheel line.
What Is a Power Steering?
If you ever tried to turn the steering wheel while the engine is off, then you know how hard that is. Car tires, which are made from rubber, generate a certain amount of friction against the surface below them. Not only does this keep your car from sliding out of bends, but it also makes turning the steering wheel hard. This is more noticeable when the car is standing still or driving slow. To make driving easier, car manufacturers install systems that help turn the wheel, known as power steering.
When looking at cars in general, there are two common steering assistance, of which the hydraulic power steering is more widespread. Here, a hydraulic pressure generates an additional force that pushes the wheels left or right, depending on your steering inputs. The central part of this system is a hydraulic pump that uses engine rotation to pressurize power-steering oil. After leaving the pump outlet, pressurized oil goes through a series of connecting pipes and tubes until it reaches the steering rack. Inside the rack, there is a rotary valve between the pinion and the steering column that controls the pressure between the left and right side of the steering rack.
Some newer cars use an electric power steering, with a direct-current electric motor mounted to the steering column or the rack itself. This system uses a torque sensor mounted over the pinion that measures the force you are applying to the steering wheel. Based on this value, the electronics of power steering decide on how much assistance it should generate. When compared to hydraulic variants, these systems offer better efficiency, have fewer parts, and are more reliable.
How to Check the Oil Inside the Power Steering System?
If there is a noise present when turning your steering wheel, the first thing to check is the power-steering fluid level. Just like any other hydraulic system, the power steering also has an oil reservoir somewhere inside the engine bay of your car. As it sometimes can be hard to spot it in cramped spaces, look for a cap with a steering wheel symbol on it. The fluid level should be between minimum and maximum marks, or the reservoir should be more than half-full, in case there are no visible markings. If the level seems low, top it off and see if that makes any difference.
Another thing to check is the color of the power-steering fluid, as this will tell you if the correct fluid is inside the reservoir. A fluid that is red indicates automatic transmission fluid, or ATF, which is fine for most modern cars. However, some European manufacturers use Pentosin inside their power-steering systems, which has a distinguishable bright green color. Check the owners manual to see what is the correct fluid type for your car, as using the wrong one can damage the power steering system.
What Else Can Cause Power Steering Whine?
Besides insufficient amount or wrong type of fluid, there are several other common issues that may cause power steering noises. For a start, check all components for any traces of oil, as this is a clear sign of a leak. When the hydraulic system doesn’t seal properly, not only does it let the oil out of it, but it also allows the air to enter inside it. This leads to a formation of bubbles within the power-steering fluid, resulting in a prominent whining noise under loads.
Another usual failure point is a power-steering pump itself, which uses engine power to spin and generate fluid pressure. Inside it, there are a series of movable vanes that can wear out or get damaged, upsetting the fluid flow within the pump housing. If this happens, it will again result in bubbles inside the power-steering fluid, just like it would if there is a leak. To verify this, remove the reservoir cap and look if there are any bubbles while a helper is turning the steering wheel left and right.
To make power-steering systems more durable, some manufacturers install a filter at the bottom of the fluid reservoir. Its only purpose is to catch any dirt or metal shavings before they cause damage to the system. However, this filter can clog-up and obstruct the flow of the fluid, especially when owners have skipped regular fluid flushes. As a result, the power-steering pump will struggle to generate enough flow, which will cause noticeable noises when turning.
What About Mechanical Components?
Although most times related to power-steering issues, noises that happen when you turn your steering wheel can also result from a mechanical issue. Any knocking or clunking sounds from the front are an indicator of possible wear of suspension or steering components. Some things to look for include play within tie rods, loose ball joints or broken suspension arm bushings. However, have in mind that most of these failures will not only produce unusual sounds when turning but also when going over bumps.
While turning the steering wheel, you are pushing several suspension parts around their axis, and making them rotate left or right. Among these components are ball joints and strut mount bearings, which must be free and move with no resistance. If any of them is jammed or blocked, it will cause a significant drag to the steering and make it harder. This can result in squealing and screeching noises while turning, but it can also cause a whine as the power-steering pump struggles with high loads.
The easiest way for checking for possible worn or stuck suspension components is by raising your car in the air. With front wheels free of any loads, you should be able to turn them left and right with no effort. If there is a noticeable counterforce or drag, you might have a jammed ball joint or bearing. Besides this, check for any play or knocks between parts that are connected together using a crowbar or a suitable lever.
Any noises that appear when you turn the steering wheel of your car are a telltale sign of an upcoming problem. Whining sounds are in most cases related to the power steering system, which can be as simple as low fluid level. Still, there are other issues that can lead to power-steering whine, which include faulty pump or fluid leaks. Besides this, you can also hear knocking or squealing noises, caused by worn or jammed suspension and steering parts.
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