Car is Squealing When Driving

The squealing is caused by stuck partially-applied brakes or worn-out brake linings. The linings are designed to squeal over time as if saying "replace us" to the motorist. But there might be alternative common causes.

The noise can also result from damage to other brake components like the rotors, caliper, or even an axle seal. Alternatively, it can be an issue from under the hood, like a slipping serpentine belt.

Watch out: The squealing noise can cause serious safety issues if it has been around for a long time. Since this type of noise is mostly brake-related, your brake pads, rotors, or calipers might slowly deteriorate. This can result in brake-related problems and failures.

The car isn’t working properly if it’s making a squealing noise; if you’re hearing this type of noise while driving, backing up, or braking, schedule a maintenance check-up. Here are some of the main risks:

Transmission problems: A squealing noise can result from an axle seal leaking. If the axle is losing oil, it’ll cause the transmission fluid to drop to the point the transmission starts slipping. If this progresses even further, the transmission can get permanent damage.
Brake Issues: Squealing noises commonly point to brakes, meaning the pads are beyond the point of replacement and should be checked ASAP. The squealing is specifically a result of the friction of deteriorated brake pads on the discs, causing overheating. Overheated brakes lose effectiveness and could cause a loss of braking power.
Health Concerns: Excessive friction and overheating on the brakes can affect the tires. The burning rubber smell from the tires can produce harmful fumes that are hazardous to breathe.

The most common causes for a car squealing when driving

Here are the most common issues causing your car to squeal when driving:

Axle seal leaking: This happens when the seal around the axle loosens up or cracks, resulting in a loss of gear oil or transmission fluid. This can progress into critical damage to the transmission or differential. The leaking fluid can also seep into the brakes, damaging them and reducing vehicle control. In any situation, a squealing noise commonly happens.
Faulty brake caliper: A greasy and sticky brake caliper will be partially applying the vehicle’s brakes. This means your vehicle’s brake pads are slightly pressuring the brakes as you drive. Consequently, there’s extra friction happening constantly, resulting in deterioration and squealing noises while the vehicle moves.
Brake pad wear: Brake pads slowly deteriorate over time. When a brake pad is at the point of replacement, it intentionally releases a squealing noise that doesn’t stop until you replace it.
Damaged brake rotors: A damaged brake rotor can have an uneven surface, hot spots, and even heat cracks. At this level of damage, the rotors cause extra stress on other brake components, commonly resulting in squealing noises, vehicle vibrations, and bad braking efficiency.
Slipping Serpentine belt: A slipping serpentine belt or timing belt can cause squealing or squeaking noises in a car due to friction and misplacement. If the belt is loose, and slips, it can cause extra friction, leading to a burning rubber smell and a squealing noise as the belt deteriorates. The power steering pump depends on the serpentine belt, so if the belt slips, it can also cause issues in the power steering system, which leads to a squeaking sound in some cases.

When/where exactly is the squealing noise happening?

The location where the noise is coming from could indicate what component might be the culprit. Pay attention when the squealing noise starts: is it when braking? After turning the A/C on?

Here are common locations/situations where a squealing noise might happen in your vehicle:

When turning the car

When turning the AC on and accelerating

Frequently Asked Questions

Q: Are your car's brake pads old?

The brake lining wear indicator is the most common reason why cars make squealing noises. This part purposely makes these types of noises to indicate to the driver that the brake linings are too thin and worn. At this point, replacing the pads with new ones is better.

Q: Are you noticing steering wheel vibrations?

Commonly, damaged brake rotors can render squealing noises in a car. As well as making squeaking noises, this problem can cause the car's steering wheel to vibrate slightly.

Q: Do you notice leak spots behind the vehicle?

An axle seal leak can produce squealing noises in a car. This crack occurs because of built-up pressure from clogged vents or seals that fail due to bearing or axle wear. Additionally, built-up motor oil on the rotor surface, a bad wheel bearing seeping grease into the braking surface, or rear brake shoes can add to the factor. The issue can also be leaking power steering fluid.

Q: Is your car braking on its own without you pressing the brake pedal?

Sometimes, a car can have partially-applied drum brakes and a sticking caliper. As a result, the car lightly brakes even if you're not pressing the brake pedal.

Q: Are you using low-grade brake pads?

Your car's rotors might have a few heat-caused cracks, which commonly accompany squealing noises. Anything that can cause rotors to overheat can push for this issue, which occurs more often on cheap brake pads.

Q: Do you commonly drive over dusty terrain?

Squeaky and squealing brakes can be a sign of worn pads, brake dust, faulty brake material, or in some cases, even aftermarket brake pads.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a squealing noise issue

The most common cause: Worn brake pads

The most common reason for a car making squealing noises is because of worn brake pads. The pads can deteriorate and rub incorrectly on the brake discs and rotors, causing a squealing noise.

Brake pads are designed to squeal when they wear out beyond recommended measures. They’re basically screaming “Change us.”

Origin of the sound: The wheels.
Symptoms it causes: Apart from the squealing noise you might notice, weak braking, brake warning lights on the dashboards, and burning rubber smells.
High risk of priority: The brake pads can keep wearing out until they completely malfunction, making your car’s brakes non-efficient

What exactly is a brake pad?

A brake pad is a little pad-shaped component on the braking system that, when pushed against the brake discs, creates friction. This friction forces the vehicle to reduce speed until it eventually stops or when the driver stops braking.

Key function: The key function of the brake pad is ensuring the vehicle stops evenly and effectively. Therefore, it’s essential to keep the pads in good condition on all wheels to prevent the vehicle from pulling to one side or losing the braking ability.

Although the brake pad is the most common cause of squealing sounds from a vehicle, it’s not the only one. Many other brake or electrical-related components in a car can cause squealing sounds.

Go safe: Ask for a mechanic to inspect your vehicle to track the squealing sound’s location and how it affects other components. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to find if anything is preventing the car from working as expected. In this case, mechanics examine different parts of your vehicle to track where the squealing noise is coming from and what’s causing it. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a brake pad service

Let’s see how a vehicle inspection defines the car service needed to fix a brake pad problem causing squealing noises.

In this example, the technician found that the brake pad was worn out. The brake pad is essential for the vehicle’s braking performance, and it works directly with other brake components like rotors, discs, calipers, etc.

In this scheduled service, the customer stated their car was making a squealing noise, especially when backing up the garage. Brake pads commonly cause squealing sounds on purpose to alarm the car owner.

If the brake pads are not replaced, the squealing noise can become louder and more frequent. As the pad deteriorates, it’ll lose its material, which is supposed to be friction against the discs. Without the friction material, the brake pads start rubbing metal-on-metal, causing serious damage to the brake system.

With these findings, the technician will also take a look at the brake rotors and calipers. Then, they'll plan a fix for the whole system.

The image below shows the worn brake pad.

Brake Pads Are Thin

In this case, the mechanic put the “Immediate Action” tag on the brake pad. They also recommended replacing the brake discs since they got worn out due to the harmful friction.