Your car often warns you before it fails, and one of its most common warnings is a noise. The problem is that "it's making a weird noise" tells your mechanic nothing, and no noise can be diagnosed by its sound alone.
These are five common noises, what they usually mean, and when you need to stop driving. And first, the most useful part: how to describe a noise so people understand you.
A noise, described well
How to describe a noise
Before going to the shop (or asking Juan), pay attention to these four things. With that, your mechanic is halfway there:
When does it happen?
When braking, turning, starting, going over a pothole, only when cold, only at a certain speed.
Where does it come from?
Front or back, one side, the engine, under the car. If you can, have someone listen from outside, somewhere safe and at walking speed.
What does it sound like?
Squeak, squeal, click, clunk, hum, grinding. You don't need the technical term: compare it to something you know.
Does it change with anything?
Whether it rises with road speed or engine RPM, whether it changes when turning or with the road surface. If you can, have a passenger record it on a phone; never do it yourself while driving.
1. Squeak when braking
Many brake pads have a wear indicator: a metal tab that rubs the rotor and squeals when there's little material left. It's a high-pitched noise that shows up when braking, designed on purpose so you hear it.
It's not always that. Pads also squeak from moisture (common in the morning, it goes away after a few stops), dust, or glazing. That's why it's worth having them checked: the mechanic measures the thickness and tells you if they need replacing.
What to do: have them checked soon.
If it grinds like metal on metal, don't wait: take it to the nearest shop now, driving slowly, or have it towed. If the pedal feels soft or sinks, stop driving: call a tow truck.
2. Click when turning the key
If you turn the key and instead of starting you hear a click (or several fast ones), the battery is most likely discharged, or the terminals are loose or corroded, with that white or greenish powder.
If the dashboard lights come on bright and there's a single click, it could be the starter motor.
What to do: check (with gloves, since that powder is corrosive) that the terminals are tight and clean, and have the battery tested.
If the battery is swollen, cracked, or smells like sulfur, don't jump-start it.
3. Squeal when starting
It's the belt that drives the alternator and, on many cars, also the water pump and power steering. When it's loose, worn, wet, or the tensioner is tired, it slips and squeals, especially when cold or accelerating.
A squeal isn't an emergency, but it is a warning: a slipping belt charges the battery less, and a belt that snaps stops driving all of that at once.
What to do: have it checked.
If the battery light comes on, the steering gets heavy, or the temperature rises, it may have snapped: stop somewhere safe and turn off the engine.
4. Clicking when turning
It's the joint that carries power from the engine to the front wheels while they turn. When it wears out, it sounds like a repeated click that's more noticeable in tight turns or when parking.
It often starts because the boot, the rubber cover that protects it, has torn: the grease escapes and dirt gets in. It could also be a bearing or something in the suspension.
What to do: have it checked before it gets worse.
5. Hum that rises with speed
If it's the bearing, the hum usually gets louder when turning one way, because the weight shifts onto the wheels on the outside of the turn. If it's louder turning left, it's most likely the right one, and vice versa.
If it's worn or unevenly worn tires, the noise changes with the road surface. Run your hand over the tread (with the car parked, and carefully, in case there are wires or glass): if you feel steps or smooth patches, that's a clue.
What to do: have it checked soon.
When to stop right away
Most noises give you time. These don't: stop somewhere safe, turn off the engine, and call for help or a tow.
- A soft brake pedal or one that sinks to the floor, or metal-on-metal grinding when braking.
- A squeal followed by the battery light, heavy steering, or the temperature rising.
- A loud, repeated clunk together with vibration in the steering wheel or the whole car.
- Any noise together with smoke, a burning smell, or a red warning light on the dashboard.
“Tell me what it sounds like, when it happens, and where it comes from. I'll tell you what's most likely, how urgent it is, and what to check.”
