What's that noise? Diagnosing common car sounds before they become big problems

We’ve all been there. You’re cruising down Parramatta Road or sitting in traffic on the M5, and suddenly your car starts making a noise you’ve never heard before. Maybe it’s a squeal, a clunk, a rattle, or something you can only describe as “that weird thing it does”. It’s easy to turn the radio up and hope for the best, but when it comes to car noises, what you hear is often your car’s way of telling you something’s not right.

The good news? Many of these sounds follow a pattern, and understanding what they mean can save you a serious headache, and a much bigger repair bill, down the track. Let’s break down the most common car noises, what’s likely causing them, and when it’s time to get the experts involved.

Squealing or screeching when you brake

This is one of the most common sounds Aussie drivers report, and it’s rarely something to ignore. That high-pitched squeal when you press the brake pedal is usually a sign that your brake pads are worn down and need replacing. Most brake pads are fitted with a small metal indicator that makes exactly this noise when the pad material gets too thin. It’s a built-in warning system doing its job.

If left too long, the sound can progress to a grinding or growling noise, which means the metal backing of the pad is now rubbing directly against your brake disc. At that point, you’re looking at rotor damage on top of pad replacement: a much more expensive fix.

Don’t wait on this one. Brakes are your car’s most important safety system, and a quick inspection will tell you exactly where things stand.

Knocking or tapping from the engine

A knocking or tapping sound coming from under the bonnet is something that should always get your attention. A repetitive knocking, particularly one that speeds up as you rev the engine, can point to issues with the engine bearings, which help keep internal components moving smoothly. This kind of knock can worsen quickly and, if left unchecked, can lead to significant engine damage.

A lighter tapping sound, on the other hand, is often linked to low oil pressure or dirty oil that isn’t lubricating the engine’s moving parts properly. In many cases, this can be resolved with an oil change, but only if you catch it early.

The rule of thumb here is simple: if your engine is making any unusual knocking or tapping sounds, get it checked as soon as possible. The longer you leave it, the more expensive the outcome.

Grinding when changing gears

A grinding sensation or sound when you shift gears, whether you’re driving a manual or an automatic, usually points to a gearbox or clutch issue. In a manual car, grinding can indicate a worn clutch that’s struggling to fully disengage, or synchromesh problems inside the gearbox itself. In an automatic, a similar grinding or shuddering might suggest transmission fluid is low or degraded, or that internal components are wearing.

Transmission and clutch repairs can be on the pricier side, but catching the issue early nearly always means less damage and a lower repair cost. If your car is grinding through gears, it’s worth booking in for a diagnostic sooner rather than later.

Rattling underneath the car

A rattling sound from below, especially over bumps, speed humps, or uneven surfaces, is often related to your steering and suspension system. Worn shock absorbers, loose tie rods, or deteriorating bushings are common culprits. These components work hard to keep your tyres in contact with the road and your car stable through corners, so when they start to go, handling and safety can be affected.

Another common cause of rattling underneath is a loose or cracked exhaust component. A rattling exhaust is usually more noticeable at idle or low speeds and can sometimes be accompanied by a deeper rumbling sound when you accelerate.

Either way, it’s worth having a mechanic take a look underneath. What sounds minor can sometimes flag a more significant issue with your car’s ride and handling.

Hissing after you switch off the engine

A hissing sound that appears after you turn off your engine is worth paying attention to. It can be a sign of a coolant leak, perhaps from a hose, the radiator, or the coolant reservoir, where hot coolant is coming into contact with hot engine components. It could also indicate a vacuum leak somewhere in the engine system.

Overheating is one of the fastest ways to cause serious engine damage, so if you notice this sound alongside a rising temperature gauge or steam from under the bonnet, pull over safely and get it looked at right away.

Clicking when you turn

A clicking or popping sound that appears specifically when you turn the steering wheel (often more noticeable at low speeds in a car park) is a classic symptom of a worn CV (constant velocity) joint. CV joints are part of your car’s drivetrain and allow the wheels to receive power while still being able to turn and move up and down.

A worn CV joint typically starts with a subtle click and can eventually worsen to the point where the joint fails completely, which can make the car undriveable. It’s a repair that’s well worth addressing before it reaches that stage.