Car squealing when you start, slow down or idle?

Here are some things that could eb causing all that noise.

The squealing might occur at different times, such as accelerating, decelerating and braking, or just idling. Whenever that annoying sound occurs, it's something to pay attention to and have checked out by a mechanic. There are a few possible causes for such noises to be coming from your car, and all of them might mean repairs.

Loose or worn belts are a common cause of vehicle squealing.

If your car squeals during acceleration or deceleration, it's probably a belt.

Just like humans, the age of your car plays a large role in the noises it makes. Typically, belts that have not broken might be well worn and in need of replacement – and this becomes apparent during acceleration. Certain belts – like the timing belt – are under extra pressure during acceleration.

The serpentine belt is one in particular that does a lot of work. In many newer cars it replaces the numerous v-belts that  are usually in place for all the different systems in your car, including the power steering pump, cooling fan, air conditioning compressor, and more. 

At acceleration, all of these systems rely on that one belt a little more heavily, which could cause the belt to squeal if it's old and worn. 

A common occurrence is squealing at acceleration or deceleration whiling running the air conditioner. 

The extra stress of these two actions causes changes in the systems' needs, which affects the serpentine belt. If your vehicle's serpentine belt breaks, all the systems it powers will stop running and severe damage could be caused to the engine.

If your car is older, it might have multiple v-belts which could be squealing. One of the most common sources of squealing is if you're running your air conditioner. 

It could be that the A/C compressor belt is worn out and making noise – which means it's time for a visit to the mechanic to get it changed.

It's also probably belts if your car squeals as it idles or warms up after starting.

Maybe you're the kind of driver who just starts your car and goes, with no time to "warm up" the engine. The need to let your car idle after starting it, allowing it to warm up and achieve some sort of optimal operating temperature has been labelled a myth. 

In any case, if your car is idling and "warming up" just after starting, and the squealing kicks in, consider the weather. This is actually a problem that occurs frequently in colder regions. The car squeals when you turn it on because the belt is cold and stiff; but the squealing dissipates after the car runs for a while. 

Whether idling or accelerating just after startup, if the serpentine belt or individual v-belts (depending on your car) are worn or loose, they'll probably squeal and should be replaced. You'll want to look at the timing belt as well, if it hasn't been looked at or changed recently.

An old or failing alternator can make squealing sounds.

The alternator pulley could be the culprit.

The noise is undeniably annoying, and for good reason. A loose or slipping alternator pulley could mean bigger problems in the future if you don't get it fixed. Additionally, the alternator has bearings that allow the rotor to spin and keep circulating electricity. 

If these bearings get old, dirty, worn out they are prone to make a loud squeaky grinding noise. When the bearings fail entirely, the rotor can't spin and you'll find yourself stuck without power and a dead battery.

If your car squeaks or squeals while turning the steering wheel, it's probably the steering system.

If your car squeaks or squeals every time you turn a corner and let everyone know you're coming, then it's probably a good guess that it's something to do with the steering.

The culprit could be one of several possibilities. It might be something as simple as low power steering fluid. Check the fluid level, top it off if necessary. 

If the noise persists, take your car to a mechanic to have the power steering fluid drained and replaced, because it might be contaminated – which could mean other issues.

If a suspension or steering component doesn't get adequate lubrication, it could cause a squeak or squeal when the steering wheel is turned. Tie-rod ends, seals, ball joints and universal joints need lubrication. 

If they dry out or get girt and dirt in them, it could cause noise. A mechanic should be able to identify the problem and recommend a repair.

Sometimes steering squeaks and squeals are as simple as tire noise on certain surfaces (like turning a corner on smooth concrete).

It should be pretty easy to tell if the squealing is coming from the brakes.

Brakes squealing is their friendly way of telling you it's time to get them serviced.

Believe it or not, brakes are designed to squeal when they start to wear out. That annoying squealing sound means you've still got time to get them replaced and not spend a fortune. 

Simply pushing the brake pedal will initiate the noise, and that's pretty much a good clue. Sometimes speed makes a difference, but brakes that need service will usually squeak or squeal at any speed. 

Eventually they'll screech and shake and grind themselves into oblivion. Brakes squealing is really when you should just have the brakes checked. 

If you wait until there is grinding or shuddering and shaking whenever you use the brakes, the squealing has probably by now gone away and been replaced by these other hideous indications that you're in for a full brake job – maybe right down to the rotors.