Troubleshooting: What’s that rattle?

Cars and trucks contains thousands of individual parts, all designed to move in harmony with one another to propel you down the road. Naturally, noises will occur on a vehicle, but you will generally know when something doesn’t sound right. The following list is by no means definitive, nor is it intended to be a substitute for an actual mechanical inspection. When your vehicle is making a new noise or one that doesn’t sound right, it is best get it to a mechanic as soon as possible to avoid further damage or problems.

High-pitched Whine or Squeal when Accelerating

If you hear a high-pitched whine or squeal coming from the front of the engine (or side of the engine on vehicles equipped with front-wheel drive) when you accelerate, the most likely culprit is a failing drive belt, fan belt, or serpentine belt. These rubber belts, powered by the crankshaft pulley at the bottom of the engine, spin other pulleys on the various engine accessories (like the alternator, power steering pump, etc.). When the rubber teeth on a belt starts to go bad, the belt will start to slip as the crankshaft pulley tries to turn it. This slipping can create a high-pitched whine or squeal as you accelerate. This sound often signals that a new belt is needed or there is a problem with one of the engine accessories.

Clicking Noise or Rattle when Turning a Corner

On front-wheel drive vehicles, a clicking noise or rattle when turning a corner is usually caused by bad CV joints (joints that help the driveshaft turn your vehicle’s wheels).

Light Tapping Sound Coming from the Top of the Motor

A faint tapping sound coming from the engine could indicate serious problems related to engine oil pressure. The problem could be as simple as the engine needing a quart of oil. But if the oil level is sufficient, the trouble could be a failing oil pump or a bad lifter. Either way, you’ll need to consult a mechanic immediately.

Knocking Sound Inside the Engine

A pronounced knocking sound usually means that you’re about to spend a whole bunch of money repairing your engine. This noise often means that your engine has “thrown a rod” (piston rod), meaning one of the rod bearings has failed, allowing the piston rod to jump around inside the cylinder.

If you hear this type of noise, shut the engine off immediately. A good mechanic can usually save the engine, provided the damage isn’t too severe. However, if you try to drive the vehicle with a rod knocking, the pressure that builds inside the cylinder can actually force the piston through the side of the engine block. Should this happen, you’ll have to buy another motor.

No matter what type of knock or rattle you hear, it’s always best to avoid driving the vehicle until you drive it or tow it to a mechanic to determine what the problem is.