It's no surprise that vehicle engines are noisy machines. Most cars use carefully controlled explosions to create the mechanical energy necessary to travel at high speeds, and this violent process is anything but quiet. Manufacturers carefully engineer their vehicles to reduce this noise as much as possible, but there's no such thing as a perfectly silent internal combustion engine.
However, some sounds can indicate trouble. If you've driven your car for a while, you're probably used to its normal day-to-day noises, so it's easy to tell when a new sound pops up. This guide will help you understand three of the most common noises you'll hear from under your hood and how you can repair them.
1. Belt, Pulley, and Tensioner Noise
Your car channels the energy from combustion into turning a driveshaft. Unfortunately, it's not easy to plug a giant, rapidly spinning shaft into accessories such as your water pump or air conditioning compressor. Instead, your car transfers energy from the driveshaft to these components by using a system of belts, pulleys, and tensioners.
These components spend their lives spinning rapidly, so it's no surprise that they tend to wear out over time. You'll typically first notice a problem with them when you hear squealing, squeaking, or even knocking sounds. If you hear these noises from your engine, it's best to repair them as soon as possible, since a catastrophic belt failure can leave you stranded on the side of the road.
2. Smog Pump Failure
The smog pump (or secondary air pump) serves two purposes: it adds clean air to your exhaust and helps to get your catalytic converter working more quickly. Your secondary air pump (SAP) only runs when your car is cold, so it's unnecessary after the first few minutes of operation. Some SAPs may also run when you shut your car off.
These devices generally produce a noise that sounds like a vacuum cleaner or a fan. However, a failing air pump may become much louder than usual. If you can hear a loud, blower-like noise from your engine bay that goes away as your car warms up, your secondary air pump may be failing. A bad pump will eventually trigger a check engine light and cause you to fail state emissions tests.
3. Power Steering Whine
Most cars use hydraulically-controlled power steering systems. These designs rely on a pump to move hydraulic fluid through the system. It's normal to hear some noise when you turn the wheel to its lock position, but you shouldn't hear much (if any) noise when simply turning the wheel left and right. If you hear a whine when moving the wheel, you may have a power steering problem.
Although this noise may be due to a bad pump, a more common cause is low power steering fluid. Topping up the fluid will solve the immediate problem, but be sure to have a mechanic evaluate your power steering system for leaks as soon as possible.
If you need any of these car repairs, contact an auto service in your area.