A braking system is one of the most important safety features in a vehicle. It is responsible for stopping the car when the driver wants to stop.
While the braking system is bound to make weird noises with time, it’s important to know the type of sound the system makes in order to help you fix it.
If you hear a whooshing sound when stepping on the brake pedal, then the possible culprit, in this case, could be a brake booster. It could be that the brake booster silencer/filter is worn out, fallen apart, or pushed all the way down.
In this guide, I shall be looking at some of the most common causes of whooshing sound when you step on the brake pedal, as well as different ways you can fix this problem.
- Problem with the brake booster
- A hole in the vacuum hose from the brake booster
- Air leaking from the master cylinder to the brake booster
Problem with the Brake Booster/Vacuum Servo
A vacuum servo is a device that uses vacuum pressure to assist in operating a vehicle’s power brakes. The vacuum servo is attached to the brake pedal and uses engine vacuum to help apply the brakes when the pedal is depressed.
When the brake pedal is depressed, a plunger in the vacuum servo pushes against a diaphragm that opens a valve.
This allows a vacuum from the engine to enter the servo. The vacuum pressure helps to push a piston in the servo, which in turn pushes against the brake master cylinder and applies the brakes.
Vacuum servos are used in many vehicles with power brakes, and they can wear out over time. If the servo is not functioning properly, it can cause the brakes to feel spongy or unresponsive.
In some cases, the brake pedal may even sink to the floor if there is a problem with the vacuum servo.
If the brake booster is faulty, you may hear whooshing noises when you depress the brakes. Additionally, if you just replaced your brakes, it could be that the brake booster was pushed way all down when bleeding the brakes.
A Hole in the Vacuum Hose from the Brake Booster
A hole in the vacuum hose from the brake booster can cause a whooshing sound when you step on the brake pedal. This is because the vacuum pump is not getting enough vacuum from the engine to operate correctly.
You can try to repair the hole in the hose, but it is likely that you will need to replace the hose entirely. If you have a mechanic look at it, they can determine if the hose can be repaired or needs to be replaced.
Air in the Brake Lines
Another potential cause of a whooshing sound when stepping on the brake pedal could be due to air in the brake lines.
Besides the whooshing noise, air in the brake lines can cause several problems with your brakes, including decreased stopping power, longer stopping distances, and a softer brake pedal.
If you notice any of these symptoms, you should bleed your brakes as soon as possible to get rid of the air in the lines.
This can usually be fixed by bleeding the brakes. If you notice that your brake pedal is spongy or soft, this indicates that there may be air in the lines, and you should have it checked out as soon as possible.
Air Leaking From the Master Cylinder
Air leaking from the master cylinder to the brake booster can cause a whooshing sound when the brake pedal is depressed.
This condition is often caused by a faulty master cylinder, although it can also be caused by a leak in the brake booster or the vacuum hose that supplies vacuum to the booster.
If you hear this sound, have your vehicle inspected by a qualified technician as soon as possible.
How Does Brake Booster Work?
A brake booster is usually located between the master cylinder and the firewall. The booster uses either vacuum or hydraulic pressure to assist in applying the brakes.
When you step on the brake pedal, it activates a plunger in the master cylinder which pushes fluid through the system and into the booster.
The booster then amplifies this force and applies it to the braking system. This helps reduce the amount of effort needed to apply the brakes and can also improve braking performance.
There are two main types of brake boosters: vacuum and hydraulic. Vacuum boosters use an engine vacuum to create additional force, while hydraulic boosters use pressure from the power steering pump.
Both types of boosters can improve braking performance, but hydraulic boosters tend to be more reliable and provide better-stopping power. Vacuum boosters can be less reliable, especially in cold weather, and may not offer as much force.
What is the Cost for Brake Booster Replacement?
The average cost for replacing brake booster is anywhere between $325-$1250. You will pay between $100-$200 for labor costs, while the vehicle parts can cost you as low as $100 up to $900 (or more).
The most common reason for brake booster replacement is due to a leak. If you have a large leak, it will need to be replaced immediately to avoid damaging your brakes. Other reasons could be due to wear and tear or an accident.
If you are unsure why your brake booster needs to be replaced, you may ask your mechanic.
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- How Much Brake Fluid Do I Need
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If you need to have the entire braking system replaced, the total cost could be as high as $1,500.
You can typically save on the cost of this job by doing it yourself, but it is important to note that it is a fairly tricky task that should only be attempted by experienced mechanics. If you are not confident in your ability to replace the brake booster, it is best to leave this job to the professionals.
Can You Drive With A Leaking Brake Booster?
No, driving with a leaking brake booster is not safe. The booster helps to provide power assistance to the brakes, so without it, the car’s braking performance will be significantly diminished. This can lead to reduced braking ability and increased stopping distances.
Additionally, brake fluid can leak out of the booster and onto other parts of the braking system, leading to corrosion and other problems. 
Therefore, it’s important to have any leaks in the brake booster repaired as soon as possible.
Final Thoughts
When it comes to your car’s brakes, it is always better to be safe than sorry. With that in mind, it’s important to know the signs of brake trouble so you can nip any issues in the bud before they turn into bigger problems.
If you are not sure whether or not your brakes are in good working order, it is best to have them checked by a professional.
By ensuring that your brakes are properly serviced and maintained, you can help avoid costly repairs or replacements down the road.
Sources:
https://oldschool.co.nz/index.php?/topic/79484-whoosh-sound-when-pressing-brake-pedal/
https://www.repairsmith.com/i/blog/brake-booster/
Hi I’m Marshall based in 1478 Doctors Drive Santa Monica, CA. I’m your DIY Car Repairman with more than 5 years experience in automobile repair, a skill I learned from my old man.
I started this blog to share my experience on both simple and technical aspects of your car.