What’s that rattling noise in your car? A quick guide.

Your car is able to make a number of insanely annoying and unnerving noises. These include squeaks, squeals, knocks, thunks, grinding sounds, buzzing, sighing, clanking — and our personal favourite, the rattle.

When a rattle strikes, this quick guide is designed to point you in the right direction.

Two key questions — where and when?

Knowing what part of the car the rattle is coming from is a great first step in diagnosing the cause.  Obviously, this is much easier if the noise appears when the car is stationary. The exhaust is often a source of stationary rattles; the engine bay is another. We’ll look more at these in a second.

Intermittent rattles, or ones that only happen on the move, are much harder to pin down. A passenger can come in handy here to provide another pair of ears.

Just as important is knowing when the rattle appears (and when it doesn’t). Ideally, you want to know if the rattle appears when:

  • the car is stationary, moving or both
  • the car is on rough road surfaces or going over bumps
  • the engine is idling, accelerating or both
  • the engine is cold, warm or both

These are all clues for you or your mechanic.

If you’ve got at least some idea of where and when, let’s get into some of the common causes of rattles.

Cause one: loose objects or cabin fixtures

It’s surprising how often a rattling noise turns out to be nothing more than something jiggling about in the car’s cabin. Cups in cupholders, pens in gloveboxes, coins, keys…the list is endless. Hard plastic surfaces in your car can act as a nice sounding board, magnifying all tiny rattles into bigger ones. Likewise, the boot can be another treasure trove of rattly objects.

The car’s internal fixtures will often rattle too, including windows, speakers, fascia and so on.

These are the best type of rattles as they are so painlessly resolved. The only bad news is that they often only start once you’re at a certain speed, making them hard to trace.

Cause two: the exhaust system

If there’s a rattle coming from under the car when you’re driving, it may be your exhaust. This is usually because a mount or bracket is failing and the exhaust is jiggling around, or because something is touching the exhaust system.

Alternatively, if the rattle from under the car is worse when you start up, it could mean that your catalytic convertor is on the way out. In this case, the rattling results from bits breaking off the mesh inside the convertor.

Cause three: the suspension

Rattling noises that appear when you’re driving over bumps, or on uneven surfaces, are often down to the suspension. These rattles can disappear once you speed up a bit or when the going gets smoother.

The culprits may be the drop links (e.g. if they’ve snapped), worn bushes or corroded shock absorbers.

Cause four: the transmission

Rattling noises on acceleration can be due to an unhappy transmission. For example, low levels of transmission fluid can lead to rattling — and that’s something that needs swift attention.

If your car’s an auto, a rattle that appears with low speed acceleration can mean the torque convertor is grumbling and might be nearing the end of its life. In some manual cars, it could be the DMF (dual mass flywheel). If that’s the case, the rattle should disappear when the clutch is depressed.

Cause five: something in the engine bay

Where do we start? Rattles coming from under the bonnet have many causes and are beyond what we can describe in a quick read. They include things like ignition system faults, faulty ignition timing, drive or timing belts, insufficient oil pressure, faults with valve lifters and so on.

Unless you’re pretty clued-up mechanically, diagnosing engine bay rattles via blog post isn’t straightforward, so we think a better option is to seek out expert advice.

The Welsh VW Specialist blog covers a wide range of automotive topics, from the contentious to the light-hearted. We are an independent garage specialising (as the name suggests!) in all the VW group marques, including Audi, Volkswagen, Skoda and SEAT. Welsh VW Specialists provide services, repairs and MOTs, delivering a main dealer level of care at affordable prices. To book your vehicle in, or for any enquiries, get in touch.