10 unwanted car sounds and what they mean

Car exhaust

Knowing the causes of odd car sounds will help you work out whether the problem is big or small, and how soon you should get the problem checked out. If you’re not sure whether your car’s sound is the result of a serious problem, stay safe by asking a reputable mechanic for advice straight away.

1. Clunking

If your car makes a clunking sound when you use the brakes, it could mean there is significant wear or damage to the brake discs, calipers or pads. If the clunk happens when you drive over bumps, there might be a problem with your car’s suspension, or part of the exhaust could be loose. However, if your car clunks when you’re turning corners, it could be a problem with the steering, wheels and tyres, or a worn-out wheel bearing.

2. Grinding or whirring

A grinding or whirring sound from your car’s gearbox might point to a problem with the clutch thrust bearing, or the clutch itself (in a manual), or a problem with the shafts and gears inside the transmission. If the grinding or whirring is coming from under the car, it could be from the differential(s) or gearbox, which might be low on oil, or from a universal or CV joint or wheel bearing. Grinding when you use the brakes can suggest worn-out brake pads – the metal backing of the pads is grinding on the brake disc rotors. Your brakes won’t work well, and the metal-to-metal contact will quickly damage the discs.

3. Hissing

A hissing sound from under the bonnet suggests there is a fluid leak, which is getting onto a hot part of the engine, such as radiator coolant leaking onto the engine block or exhaust manifold. If the hissing happens when you accelerate, it could instead be a vacuum leak from one of the small hoses around the engine’s air intake.

4. Knocking

A knocking sound from your engine is usually a sign something is seriously wrong – get it checked out as soon as you can. An expert will be able to tell you if it actually is a big problem with the engine’s insides, or something that’s more easily fixed. There is an engine condition that’s sometimes referred to as ‘knocking’, but it actually sounds like a faint metallic ‘ping’ when you accelerate, and can come from an engine that’s poorly tuned, or running on the wrong fuel, with too low an octane (or Research Octane Numbers (RON)) rating.

5. Banging, popping or spluttering

A loud bang from your exhaust pipe is the sound of a backfire, which happens when unburned fuel comes out of the engine and ignites in the tailpipe.  You might have a vacuum or exhaust leak somewhere, or a problem with the catalytic converter – in an older car, it could suggest that the engine is out of tune. If the popping or spluttering is coming from the front of the car, it could indicate a problem with the engine’s fuel, ignition or exhaust system, caused by a blocked fuel filter, old spark plugs, or a malfunctioning catalytic converter.

6. Rattling

Rattles from underneath your car indicate something is loose, or that something has lodged itself down there. It could be that part of the exhaust system or suspension has come undone, and should be checked out as soon as possible.

7. Roaring

Roaring or a plain noisy exhaust when you accelerate usually points firmly to an old exhaust system that has rusted or become damaged to the point that a muffler is no longer doing its job to keep the car quiet. An exhaust problem won’t usually stop your car, or cause further damage, but it could be letting exhaust emissions into the cabin, so should be checked out straight away.

8. Tapping or clicking

A tapping or clicking sound from under the bonnet might mean your engine is low on oil, which is easy to check and top-up. On an older engine, it could suggest there is a problem with the valve train. If your car has done a lot of kilometres and/or has not been serviced regularly, it might simply indicate that your engine is worn-out, though some engines will continue happily for a long time with a top-end tick, especially if the sound goes away when the engine warms up, or in warmer months.

9. Whistling

A whistling from under the bonnet might mean your engine has a vacuum leak from one of the hoses around the air intake – these can be tricky to trace, but are usually simple to fix.

10. Squealing

A squealing sound from under the bonnet of your car is one of the most common – and easily fixed – car sounds. It means one of the belts that drive accessories such as the air conditioning or power steering from the engine is slipping on a pulley. A good mechanic will have this fixed for you in minutes. If the squealing comes from the wheels when you use the brakes, it could mean you have worn-out brake pads or another brake system problem. However, if the squalling is coming from your tyres, you should turn your cap round the right way and go a bit easier on the accelerator.

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