Strange Vehicle Noises Explained

You know what your own vehicle normally sounds like.

Whether it is a car, van or motorbike, you get used to the usual engine note, tyre noise and small rattles that come with everyday driving.

That is why a new clunk, scrape or rumble tends to stand out.

The important thing is not to jump to conclusions about the cause. The same sound can come from several different faults, and what matters most is when it happens, where it seems to come from and whether anything else has changed at the same time.

A current MOT certificate also does not guarantee that a vehicle will remain safe and roadworthy until the next test.

If a new noise appears and you cannot explain it, it is worth having it checked.

A clunk when pulling away or changing gear

A heavy clunk as you move off or change gear can make the gearbox seem like the obvious suspect.

That is not always the case.

Worn engine or gearbox mounts are one possibility because the engine and transmission can move more than they should when power is applied.

The clutch or transmission may also need attention.

Try to notice exactly when the noise happens.

Does it occur only when pulling away? Is it present in every gear? Does it happen when you lift off the accelerator?

If there is also juddering, difficulty selecting gears or a noticeable change in how the vehicle drives, mention that when you book it into a garage.

The noise alone cannot tell you which part is at fault, but the pattern can help a mechanic narrow down the cause.

A knock over potholes or speed bumps

If a noise appears mainly over uneven road surfaces, the suspension is one area a garage may investigate.

Worn suspension components or a damaged spring can produce knocks, clunks and rattles.

A loose exhaust can sometimes sound surprisingly similar.

That is why it is difficult to diagnose a noise from the driver's seat, especially when it seems to come from somewhere beneath the vehicle.

For van drivers, it is useful to notice whether the sound changes when the vehicle is carrying a load.

That can be helpful information for the garage, but it does not mean the load itself is necessarily the cause.

A metallic rattle from underneath

A metallic rattle can make it sound as though something is loose beneath the vehicle.

Sometimes that is exactly what is happening.

An exhaust component or another part underneath the car or van may be vibrating or knocking against the body.

The AA also notes that a failing catalytic converter can produce a noise similar to a loose exhaust.

From inside the vehicle, however, sounds can travel and be difficult to locate accurately.

Rather than trying to identify the part yourself, ask a garage to trace the source.

A rumble that gets louder as you drive faster

Not every warning sound is a clunk or knock.

A wheel bearing problem, for example, can sound more like a hum or rumble that becomes increasingly noticeable as road speed rises.

Tyres and other wheel-related faults can also create unusual sounds.

If the noise clearly changes with speed, tell the garage.

That pattern may be much more useful to a mechanic than your best guess at which component is responsible.

Scraping, clicking or grinding when braking

A new noise during braking deserves prompt attention.

Scraping, grinding or clicking could be caused by worn brake components or something caught near the brake disc.

If a vehicle has been standing for a while, surface rust on the brake discs can also sometimes cause temporary noise.

A knock while turning may point towards steering or suspension components instead.

Because braking, steering and suspension all affect the way a vehicle stops and handles, changes in these areas should not be ignored.

If the noise is severe or the vehicle does not feel right, stop somewhere safe and seek professional advice before continuing.

What if the vehicle is a motorbike?

The same principle applies to motorcycles, but small changes can sometimes be easier to feel as well as hear.

Pay attention to whether a noise appears under acceleration, during braking or when riding over bumps.

Areas a mechanic may need to inspect include the chain and sprockets, suspension, wheel bearings and exhaust.

Chain condition is particularly important.

An excessively loose or worn chain or sprocket can be classed as a serious MOT defect.

If the bike begins to feel different under braking, steering or acceleration, do not rely on the noise alone to tell you what is wrong.

Have it inspected.

What should you tell the garage?

Before booking the vehicle in, make a short note of what you have noticed.

Useful details include:

• when the noise happens

• where it seems to come from

• whether it changes with speed

• whether it appears when braking, steering or changing gear

• whether it is becoming louder or more frequent

• whether the handling, steering or braking feels different

A good description can help a mechanic reproduce the problem and find the source more quickly.

It still cannot replace an inspection.

Only a proper check can establish what the fault is and whether the vehicle is safe to drive.

Strange noises are often your vehicle's way of telling you that something has changed.

So, if something starts going bump on the road this Halloween, do not ignore it and hope it disappears.

The explanation is probably mechanical rather than supernatural.

But either way, it is better to find out before the noise gets any worse.

Happy Halloween!

Frequently asked questions

What does a clunk when changing gear mean?

There are several possible causes. Engine or gearbox mounts can allow extra movement when power is applied, while the clutch or transmission may also need attention. The pattern of the noise and any other symptoms can help a garage diagnose the fault.

Why does my car knock over speed bumps?

Knocking over bumps can be linked to suspension components, a damaged spring or a loose exhaust. Because several faults can sound similar, the vehicle should be inspected rather than diagnosed from the noise alone.

What can cause a metallic rattle under a car?

A loose exhaust component is one possibility, but other parts beneath the vehicle can rattle too. The AA also notes that a failing catalytic converter can sound like a loose exhaust.

Why does my car make a rumbling noise that gets louder with speed?

Wheel bearings, tyres and other wheel-related faults can all cause humming or rumbling noises. If the sound changes noticeably with speed, mention this when booking the vehicle into a garage.

Should I keep driving if I hear grinding when braking?

Grinding or scraping during braking should be investigated promptly. If braking performance has changed, the noise is severe or the vehicle feels unsafe, stop somewhere safe and seek professional advice before continuing.

What motorbike noises should I take seriously?

New noises linked to braking, acceleration, steering or riding over bumps should be checked. Areas such as the chain and sprockets, suspension, wheel bearings and exhaust may need inspection.

Does a valid MOT mean my vehicle is safe to drive?

No. An MOT confirms that the vehicle met the required standards at the time of the test. Faults can develop afterwards, so a new noise or change in braking, steering or handling should still be investigated.