If your car or truck is making any type of odd sound, it's good to have this issue diagnosed as soon as possible, in case that sound means something is wrong with a major component under the hood. Fixing any such mechanical problems as soon as possible will keep your car safe on the road, and also help to avoid more extensive repairs over time. This can also mean avoiding excessive and unnecessary wear and tear on the vehicle itself! Consider a few tips on how to diagnose needed repairs based on the noises you hear coming from your car.
Don't assume that the fan belt is the only potential problem when you hear this squeal; the engine of a car has a pulley that also works with a serpentine belt, and which guides and directs all other belts under the hood. This belt can also squeal when it becomes loose or damaged, and if it should snap, all other parts that run with belts, including the fan, alternator and various pumps, will then fail. If you check under the hood and the fan belt looks fine, be sure to inspect this engine pulley belt and have it changed as quickly as possible.
Tapping or metal to metal
If a metal to metal or tapping sound is heard under the hood, this is usually an issue with the timing. This refers to how the pistons in the engine aren't moving in sync, or at the speed they should be moving. There is a timing belt that controls their movement and which might need to be changed, or the timing itself may need an adjustment. Running the engine with the timing "off" can cause serious damage, so have this checked as soon as possible.
Consider the thumping noise you hear when you drive over a bumpy road; if you hear that same sound when driving on level pavement, the wheels may be bouncing up and down in a similar fashion. This is often the cause of a worn or broken shock or strut, or a broken or bent tie rod, as these pieces should keep the wheels in place when you drive. When they need repair or replacement, the wheels will thump, even over level pavement.
If you hear thumping when you turn a corner, this is often the fault of worn differentials that need repair, the gears that control the speed of a wheel's rotation when you turn. When these wear down, the car may "thump" around corners, and also produce some drag or resistance.