Why Is My Car Making a Clunking Noise?
Ellie Dyer-Brown, 14 days ago
5 min read
- Diagnostic
FixMyCar looks at some of the reasons why your car might be making a clunking noise.
Like banging or hissing, clunking is a common noise reported by drivers and a clear sign of a problem. This guide will help you work out what might be going wrong.
Contents
My car makes a clunking noise when it starts
In a nutshell: Your car might be making a clunking noise due to transmission problems, an issue with the starter motor, a damaged or worn suspension system, worn or loose brake components or a loose exhaust. Read on to find out how much these problems cost to fix.
My car makes a clunking noise when it starts
A clunking noise when you start your car may indicate a problem with the transmission or starter motor.
Transmission problems
There are five things to investigate regarding your car’s transmission.
1. Low or old transmission fluid
When there isn’t enough fluid to lubricate the transmission system, one of the most common symptoms is a knocking or clunking sound. Similarly, old fluid may not be able to lubricate components enough to protect them.
Transmission fluid should be red or pink. If it's any other colour, it may be too old or burnt to function, in which case you should drain the system and refill it with new fluid. This guide explains how to check and change different types of fluid.
When you top up your fluid, it’s also worth keeping an eye out for any leaks.
2. Broken or loose transmission mounts
Transmission and engine mounts are vital because they hold heavy components in place. If they become corroded or work themselves loose, you may notice a clunking sound when you turn corners because the mount is not secured correctly.
3. Malfunctioning transmission sensors
Modern car transmissions are often controlled by a computerised sensor system. When the sensors malfunction and send false information about shifting gears or changing speed, you may hear a clunking noise due to incorrect transmission regulation.
4. Broken flex plate
A flex plate is a metal disc found in automatic transmission vehicles instead of a flywheel. It connects the engine’s output to the input of a torque converter.
Flex plates can become cracked, warped or broken due to misalignment, a bad starter motor, an unbalanced engine and poor-quality parts. When this happens, one of the most common symptoms is a rhythmic clunking or grinding sound.
5. Faulty internal components
Several components in the transmission contribute to the smooth shifting of gears, such as bearings and springs. When they become worn and stop working correctly, they can cause a clunking sound.
Apart from transmission fluid, these problems all need to be assessed by a trained professional. Sometimes, a mechanic may have to remove your transmission to identify the source of the noise. Most issues can be solved by replacing the defective part, such as a faulty sensor.
How much do transmission problems cost to fix?
The average price of a transmission repair booked through FixMyCar is £250.89. For an automatic transmission diagnostic, the average price is £152.97.
Starter motor problems
A few different issues with the starter motor could be to blame for the noise.
1. Loose starter
If your starter motor hasn’t been fitted correctly and is missing a bolt, it may not be secured to the mount, which would cause a loud clunking noise when you start the engine.
2. Faulty starter
Like any component, the starter motor wears out over time and may eventually need replacing.
Signs of a bad starter include:
Unusual noises, like clunking and whirring
Engine fails to turn over
A single click when you turn the key
How much does it cost to fix starter motor problems?
Starter motor replacement is not a big job, though it will likely take several hours. Some starter problems can also be repaired; the average price is £384.39 on FixMyCar.
My car makes a clunking noise while driving
A clunking sound while driving could be caused by several things discussed below.
Suspension problems
Learn about how a car’s suspension works in this guide.
1. Shock absorbers
If you hear a prominent clunking noise when you drive over speed bumps or potholes, you probably have a problem with your suspension, especially the shock absorbers.
Shock absorbers can be mechanical or hydraulic. They convert the kinetic energy from the shock into a different form of energy, which is then dissipated, giving you a more comfortable driving experience.
When the shock absorbers wear out, it puts more strain on other suspension components, sometimes causing them to clunk against one another.
2. Damaged or worn ball joints
Ball joints are spherical bearings that connect the steering knuckles with the control arms. Like our joints, they allow smooth movement without too much friction. But when they become worn, problems develop as two components, like bones, start to move against each other - this is where the clunking noise comes from.
3. Worn control arm bushings or stabiliser bar links
Like ball joints, these components are responsible for connecting various suspension components and keeping the wheels correctly aligned. It’s easy to tell when they wear out because this almost always results in unusual noises and a less comfortable ride.
How much does it cost to fix suspension problems?
Prices vary depending on which suspension component is faulty and the type of car you drive. On average, suspension repairs cost £135.27 when you book through FixMyCar.
Loose exhaust
Another possible explanation is that the exhaust is loose, causing a clunking sound as it hits the underside of your car. As long as it hasn’t sustained any damage, it should be easy for a mechanic to secure the exhaust in place.
Find out more about car exhausts in this guide.
You should be able to tell if a loose exhaust is to blame because the sound will come from the rear of your car, particularly after hitting a bump or turning a corner.
How much does it cost to fix a faulty exhaust?
On average, an exhaust repair costs £123.36.
My car makes a clunking noise while braking
No surprises here: a clunking noise while braking indicates a problem with your car’s brakes. While this broad diagnosis is straightforward, pinpointing the exact cause takes a little more investigation.
If you’ve ever wondered how car brakes work, you can find out here.
1. Loose bolts
Loose bolts allow components to move around in ways they shouldn’t, creating thumping or clunking sounds. You can check the bolts yourself or have a mechanic do it for you - either way, this problem is easy and cheap to fix.
2. Misaligned or loose callipers
Brake callipers are a crucial part of any disc brake system. They perform two roles: firstly, acting as a bracket to support the brake pads, and secondly, converting pressure from the brake fluid into friction.
Misalignment can cause clunking - this is something to check if you’ve recently had new callipers fitted - but it’s also possible the noise could be caused by failure of the component.
Here are all the signs to look out for suggesting your brake callipers need replacing.
Brake pads and discs need changing far more frequently than callipers. However, if you continue driving on worn pads for too long, it can cause the callipers to fail, too.
A snapped calliper bracket could be to blame for the clunking sound, although this form of failure is rare. This is a brake problem you shouldn’t ignore. Contact a mechanic as soon as possible and avoid driving.
How much does it cost to fix clunking brakes?
Brake repairs cost £134.35 on average when you book through FixMyCar.
If you have any other issues with your car that you'd like to try to diagnose yourself, check out our guide on self-diagnosing car problems. The more you know about how your car works, the better.
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