why does my car whistle when I brake

When you hit the brakes, do you hear a high-pitched squeal coming from your car? The sound may be familiar, but what causes it?

Loss of Brembo Brake Booster function: If the brakes are overinflated, the brake booster loses its ability to suck up all that air and control that air under pressure. This puts a strain on the cabin’s air compression system that acts as a sonic pump for frequencies above 2kHz – meaning those frequencies can’t dissipate once they’re produced by the brake disks rubbing against the pads – this is why you hear these frequencies as whistles.

Air Leaks in Vacuum Hose System: These leaks allow atmospheric pressure inside your brake booster to decrease, which reduces the pressure inside the brake booster. This change in air pressure within the brake booster causes a whistle or a hissing noise.

Brake Caliper Reversal: If your car’s brakes are self-adjusting, they could be pulling unevenly against one of the calipers because it’s reversing itself due to wear, corrosion changes or modifications to your braking system – this puts stress on parts and increases wear rates as well as creates more noise from your wheels.


In conclusion, if you hear a high-pitched sound when you apply the brakes there is nothing to fear – although annoying, it’s typically harmless and can be fixed by servicing your brake fluid and/or replacing any defective parts within your braking system.

Frequently Asked Questions

How do I stop my brakes from whistling?

Your brakes are designed to cause the tires to grip the ground, but if you have a high-pitched sound coming from your car that sounds like a whistle or screech, then it’s time to find out why. There are three reasons why your car may be whistling when you brake: loss of Brembo brake booster function, air leaks in vacuum hose system, and brake caliper reversal.

why does my car make a high pitched noise when I brake?

When you hit the brakes, your car may make a high-pitched sound. This can be caused by three things – lost Brembo brake booster function, air leaks in vacuum hose system, and brake caliper reversal.
Steven Hatman
Steven Hatman

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