As your car or truck ages and accumulates more miles, it's likely to develop some interior squeaks or rattles, and that's perfectly normal. There are other noises, though, that can indicate trouble, or may not indicate much of anything at all. It's a good idea to keep an ear attuned to these noises and know what they mean if you hear them.

Here are some things to be aware of, and what they can mean:

  • Growling car noise: A growl that rises and falls with engine RPM can point to a low power steering fluid level, as the pump in the unit starves for lubrication. You may simply need to top off your power steering fluid, but you should also inspect the system for leaks, as repairs may be needed.
  • Ticking from under the bonnet: A slight ticking car noise is normal; it's the sound of the fuel injectors doing their job. A louder ticking can indicate lifter or valvetrain noise. Valvetrain noise by itself isn't especially worrisome — an engine can run another 70,000 miles with a noisy lifter, but you should check the oil level nonetheless.
  • Ratcheting sound from the front end: Failing CV joints on a front-wheel-drive vehicle will make a rhythmic clicking or ratcheting noise that you can hear with the windows down. A good way to pin this car noise down is to find a parking lot and drive in a circle, with the wheel racked to one side, and see if the noise gets louder as you turn in one direction compared to the other direction.
  • Noticeable clunk when you put the gearbox in gear: On a rear-wheel-drive vehicle, failing U-joints will clunk when you put the vehicle in gear, or when you step on or let off of the throttle. It's the sound of slop being taken up in the joint as you apply the throttle. On an FWD vehicle, this sort of clunk can mean worn motor mounts, although it will come from the front end. Often in FWD vehicles, worn motor mounts will also mean a vibration that gets stronger when the engine is under load.
  • Squeaky front end: Squeaks or pops from the front end as you go over bumps can point to failing ball joints. Worn ball joints will often also mean poor road manners and a lot of slop and play in the steering, with a constant correction to stay in a straight line. You can diagnose ball joints by safely jacking the front end up so that the wheels hang and the suspension has no load on it. Grab the wheel at 12 and 6 o'clock and work it back and forth, as well as 3 and 9 o'clock. See how much excessive play is in the wheel and listen for popping or cracking noises.
  • Groaning car noise: A whining or low groaning noise can come from the gearbox if the fluid level is low, or if fluid is excessively dirty and worn. This is a problem that should be addressed right away. Learn how to check your gearbox fluid properly.
  • Clunk as you apply the brakes: A calliper is misaligned or loose, or some other piece of brake hardware is loose. This is dangerous, and the vehicle should not be driven until it's diagnosed and repaired. Learn more about the components in your brake system.
  • Squealing or grinding when you apply the brakes: A squeal can mean brake pads that are starting to wear down, or it might not mean much of anything. Some brake pads' friction material are just noisier than others. Still, have it checked. A metallic screech or grinding, on the other hand, can mean that the brake pad's wear indicator is dragging on the brake rotor or that the pads are worn to the point of metal-to-metal contact. This is very dangerous; replace your pads and rotors right away, or take your vehicle to a trusted professional.
  • A click every few seconds when the AC is running: When the AC's refrigerant is too low, the compressor's clutch will cycle the compressor on and off. Low refrigerant will also be accompanied by poor AC performance, such as blowing cold only when the vehicle is in motion or musty smells coming from the vents. Recharging your system is easy with A/C Pro, though.
  • Whining or howling from the rear: A differential that's low on oil or is starting to wear can make a whine or howl that changes in pitch as you speed up.
  • Squeal or chirp from under bonnet: On an older vehicle with multiple V-belts, this usually points to a belt that's loose or an accessory pulley that's slightly skewed. Serpentine belts are equipped with a tensioner that delays this problem, but old belts can still be inspected with a flashlight. Any cracks or frays mean it's time to replace.
  • Irregular rattle from under vehicle while driving: Chances are this is a loose exhaust component or hanger. You might also notice a vibration from underneath while idling in gear with your foot on the brake.
  • Thump from the front end over bumps: If you hear a thump when you hit a big pothole, that's not at all unusual. Thumbs or clunks over small bumps can indicate a worn shock absorber, worn front-end bushings or other problems. When the vehicle's parked, push down on a fender repeatedly and see if the noise can be replicated. The vehicle should bounce no more than twice; more than two bounces can mean worn shocks. These kinds of noises can also mean worn steering components like the drag link, Pitman arm or idler arm. Lift the bonnet, turn the key to unlock the steering wheel, get a helper to work the wheel back and forth engine off and listen for any unusual noises. Also watch the steering linkage to see how much play or slop is in the components as they do their job.
  • Heavy clunking or banging noise from engine: If you hear something that sounds like someone banging garbage can lid with a hammer, that's not good at all. It can mean worn main bearings or rod bearings, or extreme oil starvation due to low oil level or low oil pressure from the pump. Pullover and check your oil level right away.
  • Humming or groaning that gets louder and changes pitch with speed: This is a tough one to pin down, but it could be an indicator of either bad wheel bearings or worn axle bearings. To further confuse things, abnormal tyre wear can also cause these symptoms. Learn more about failing wheel bearings to differentiate between the two.
  • Hissing from under the bonnet: More often than not, a hissing car noise means a vacuum leak, either from a hose or vacuum line or possibly at the head gasket. A leaky head gasket will show all sorts of other drivability problems, though.

This is just a quick overview of some of the strange noises your car might make, and how to interpret them. That doesn't mean that you should become an automotive hypochondriac, but it's important to develop an ear for this sort of thing anyway.

What noises does your car make and have you check them out? If you have any issues / bad noises in your car get in touch?