When turning at slow speeds, a knocking or clunking noise is your car’s way of telling you there is a fault with the suspension. Modern vehicles’ multi-link suspension systems include several arms, bushes, and ball joints. They all have their unique issues and ways of failing and determining they are faulty.
This article contains the most common causes I have come across in the last 16 plus years of repairing these types of faults almost daily.
Seven Causes of a Clunking or Knocking Noise When Turning at Low Speeds
Some of the causes below are very similar, especially ball joints. However, we listed them separately so you can understand each components role instead of just telling you that a ball joint might be worn.
Drop links
Drop links, also known as anti-roll bar or sway bar links, connect the shock absorber strut or wishbone to the anti-roll bar by tiny nylon ball joints. The anti-roll bar then runs from one side of the car to the other, connecting them both. The role of the drop link is to transfer the roll stiffness generated by the anti-roll bar, limiting body roll, which keeps the vehicle flat through corners.
The typical problem with anti-roll bar links is the ball joints tend to wear with repetitive excess movement from age. You can usually hear a worn drop link as a soft knocking when turning or not very loud clunking noise when going over bumps.
TrackRodendBalljoint
The tie rod end, also known as the track rod end, connects the wheel hub to the steering rack. When you turn the steering wheel, this is the part that pushes or pulls on the wheel hub. Like all automotive ball joints, the internal is a ball and socket joint.
With repeated movement over time, the socket joint wears out, and the ball element rattles. As a result, you get a knocking or clunking noise when turning the wheel. You may also experience other symptoms, such as a knock from the tie rod end under braking and an unsteady feeling when the car is driving at speed.
Bottom armBalljoint
The lower arm ball joint, also known as the control arm ball joint, connects the chassis to the bottom of the wheel hub. The ball joint on the lower control arm differ slightly from the others in that they are heavier duty because they take the most abuse when driving.
Like all ball joints, they wear out with age. Their unique symptoms are a knocking noise when turning at low and high speeds and a loud clunking noise when driving over bumps or potholes.
The good thing with lower-arm ball joints is that they are usually bolted to the control arm independently, so you can swap out the ball joint only, which makes the repair very cheap
Broken coil spring
Coil springs wrap around the strut of the shock absorber and act as a method of stabilizing the vehicle over bumps. Coil springs don’t tend to break in half, usually a few inches snaps off the bottom or top of the spring. When this happens, the spring gets caught in the spring pan or top mount; when turning the steering wheel, you’ll hear a loud clunk or twanging noise. This noise is the spring getting caught and then releasing.
You may also experience other symptoms such as the car pulling off to one side, grating noises, hearing the broken part of the spring rattle as you drive over a rough road, and visibly seeing the car has dropped to one side.
You should not replace coil springs individually but always in axle pairs. Replacing only one coil spring can lead to driving issues, such as the vehicle pulling to one side permanently.
Most importantly, I recommend that a competent person or mechanic only carry out coil spring replacement. Coil springs secure to the strut under extremely high tension. Not using a spring compressor tool before removing the top mount nut will result in serious injury.
CV joint
The CV joint or Constant-velocity joint is the ‘wobbly’ end of the driveshaft. It allows the drive generated by the car to be transmitted through the drive shafts at different angles. For example, when one wheel is on the curb and the other isn’t. As most roads also have variable camber, the car accelerates with the wheels at different angles.
When the CV joint fails, you’ll hear a few issues: a ticking at low speeds when turning, a humming noise when driving, or knocking/tapping when turning the wheel. The most common cause for CV joint failure is a split CV boot gator, causing the CV joint to dry out. The gator’s job is to keep the grease contained, so when the gator splits or cracks with age, the grease leaks.
If this is caught early, you can sometimes repack new grease and replace the gator; this knocking noise may vanish after a few minutes of driving. However, you may need to replace the CV joint if the knocking noise remains.
Suspension bush
Suspension bushes connect various moving components, such as anti-roll bars, strut mounts, or subframe bushes. Over many driving miles, these bushings wear out with the constant movement of the suspension. Suspension bushes are constructed of rubber, sometimes in a metal housing; the rubber usually dries out and cracks with age, making excessive movement and knocking noises more noticeable at low speeds.
The knocking noise is the bush moving too much and the metal frame that sits through the bush moving and knocking on the bush casing. Not all bushes can be changed easily; depending on the design, they may need to be pressed into a housing, which requires the correct tools.
Steering rack
The steering rack comes in a few different types, the most common being rack and pinion. Which is a cog connected at the steering column to a track; when you turn the steering wheel, the cog (pinion) moves along a track (rack), pushing one wheel out and the other inwards, turning the car.
There are a couple of things that usually go wrong with a steering rack:
- The rack or pinion teeth get worn over time, causing movement in the steering rack.
- There is a leak of power steering fluid from the steering rack. The rack internals dry out and fail.
- The steering rack gets damaged from an impact, usually hitting a curb or another vehicle side on.
These problems usually manifest as a knock or clunking noise from the steering rack, or you’ll have difficulty turning the steering wheel.
To check a faulty steering rack with the vehicle stationary and off, you can feel excess movement or play in the rack by moving the steering wheel from side to side.
How Do You Test Where the Knocking Noise Is Coming From?
Testing suspension components for play is pretty straightforward and can be done without a ramp. First, you’ll need to road test the vehicle with the windows down turning the wheel at slow speeds determining which side of the car is knocking or clunking.
Do not continue the if you suspect a broken coil spring; touching the broken spring could cause injury.
To test which suspension component is faulty put your hand on the item (ball joint or bush) you think might be the suspect. Getting the right angle without trapping your arm in between the wheel and fender is a little fiddly. But if you can get your arm in, have someone else gently rock the steering wheel from side to side. You’ll feel any play or knocking noises transferred through your hand. This might sound strange to say to someone that has never done this before, but you can feel the difference between a nice tight ball joint and a worn one.
Getting your hands dirty and covered in grease isn’t for everyone, so if in doubt have your local mechanic check this over for you.
Is It Safe to Drive With a Knocking Sound?
Many worn suspension components, such as worn ball joints, are picked up during vehicle inspection. Take from that what you will. But to say it is safe to drive with a knocking sound from the suspension is a recipe for disaster without knowing the exact cause.
A worn suspension bush or ball joint will be okay if you need to make a few small journeys. But, a broken coil spring could catch in the pan and cause more problems, such as a tire blowout. So, driving with that type of problem is certainly not safe.
The issue with driving with worn ball joints is the more the ball joint moves because of excess play. More friction and heat are generated, which can cause the ball joint to completely pop out of its socket, which would be equally dangerous and cause further damage to other suspension components.
Frequently Asked Questions
What Causes A Knocking Sound When Turning?
A knocking sound when turning is usually a sign of a worn suspension component. The most common parts to fail are either a worn ball joint or a failed suspension bush.
What Does A Bad Lower Ball Joint Sound Like?
A bad ball joint sounds like a deep metal tapping noise every time you drive a bump no matter how small or if you turn the steering wheel. Depending how bad the ball joint is a single tapping noise may develop into a rattle.
How Do You Fix A Knocking Sound From The Suspension?
Every suspension component on a car can be replaced. Once you have identified the correct cause of the knocking sound. Replacement is the only way to solve the issue 99% of the time.
Final Thoughts
The most common cause for a knocking or clunking from a cars suspension is a worn ball joint. The tie rod ends are the first ball joints I would check if a knocking noise when turning at slow speeds was reported.
It is possible to check and replace some of the suspension components yourself; however, after suspension components are replaced, the tracking or 4-wheel alignments will need to be corrected immediately after. Most people will not have wheel alignment gauges at home to carry this out, I don’t and I do this for a living!
