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What Does a Brake Booster Do?

CarPart  ·  May 11, 2023

What Does a Brake Booster Do?

Many of today’s drivers don’t realise they’re getting a lot of help when operating their vehicles. Power steering systems, for example, make it so drivers use less force to steer their cars. Brake boosters do the same thing for the braking system.

The brake booster is a brake component that amplifies any force you apply to the brake pedal. When you step on the pedal, a much bigger amount of pressure is applied to the brake system by that booster. It reduces fatigue and helps you brake the car faster and harder with minimal effort.

Brake boosters last a long time and rarely fail, but still, you’ll want to understand how they work and what happens when they fail. This guide will show you all of that in the following sections.

Let’s get started!

What Is a Brake Booster, And How Does It Work?

A brake booster is a component that amplifies the force you apply to your brake pedal with your foot. So, whenever your foot presses on that pedal, the booster increases the amount of pressure that reaches the master cylinder.

The brake system is a critical safety feature in your vehicle, and the brake booster no doubt helps it do its job.

When driving, you use the brakes several times, and that can be incredibly tiring if you’re taking a long trip. Imagine doing that without a brake booster – you might as well drive without power steering! 

A perfect example is the 80 series brake booster in Land Cruisers. Without the help of a powerful booster like that, your leg would get tired quickly trying to operate that truck’s brakes all the time.

Besides preventing fatigue, the brake booster keeps you safe when applying brakes quickly, such as in emergencies. Only a small amount of force from you is necessary to fully engage the brakes and bring your car to a complete stop.

Brake boosters provide similar benefits to power steering systems by amplifying your force and preventing fatigue. So, it’s no surprise that brake systems with these boosters are also known as power brakes.

These days, power brakes are a standard feature on many new car models, but not all vehicles on the road have them. If you’re driving an older model without power brakes, it’s about time to be nice to yourself. You can purchase aftermarket brake booster kits, install them in your car, and enjoy modern driving.

What Are the Different Types of Brake Boosters?

Brake boosters come in three varieties: vacuum brake boosters, vacuum pumps, and hydraulic brake boosters.

Here’s how they work:

What Are the Signs of a Failing Brake Booster?

Your brake system and booster are critical for your safety on the road. That’s why you must understand the symptoms telling you that a brake booster repair is necessary.

Here are the signs of a failing brake booster:

1. Brake Pedal Resistance

The first and more subtle sign that your brake booster is failing is when there’s added brake pedal resistance. In other words, your brake pedal becomes more challenging than usual to push when you need to slow down your vehicle.

That happens because the brake booster no longer amplifies the force you apply on the pedal. Therefore, you're not getting the help you need from it to engage the brake system.

2. Unusual Brake Pedal Movements and Positioning

Aside from the increased resistance, a problematic brake booster will also cause your brake pedal to behave unusually. 

For example, when you lift your foot off, the brake pedal might take much longer to return to its original position. That will likely happen when the brake booster’s chambers aren’t as balanced as they should be.

3. Increased Braking Distance

Another subtle sign of brake booster failure is an increase in braking distance. So, when your car takes longer than usual to stop, it’s always best to troubleshoot your main brake components first. That includes checking the brake pads and rotors for damage.

If those parts are still in good working order, then the likely culprit is the brake booster. That’s because one of several symptoms of a bad brake booster diaphragm is that it prevents those main brake components from working effectively.

That will lead to a lack of friction generated to slow the car down, increasing overall braking distance.

4. Engine Malfunction

Believe it or not, a failing brake booster can also affect the engine and cause it to malfunction.

Remember: the brake booster relies on a vacuum to amplify your braking pressure. Therefore, a failed booster can develop leaks that disrupt its entire functioning.

For example, a problematic brake booster can affect the engine’s fuel-air mixture by sucking in too much air. That will directly affect the engine’s combustion process and cause various malfunctions.

When Should I Replace My Brake Booster?

Brake boosters typically last throughout a car’s lifetime. So, most people never even need to know about brake boosters. The only exception would be if the brake booster failed and demonstrated symptoms like the ones you read about earlier.

You should always try to repair brake booster problems before considering a replacement, as it can be costly. Plus, some booster problems are easily fixable by replacing just the affected component or with necessary brake booster reconditioning.

Once you rule out those two options, you should immediately replace your brake booster.

Always check for news on vehicle recalls or known issues that might apply to your vehicle and its brake booster. Also, be sure to rely only on official information to avoid misunderstandings, like the supposed Ford Edge brake booster recall that was not a recall at all.

Can You Drive Without a Brake Booster?

No, you cannot drive without a fully-functioning brake booster. Even if the rest of your vehicle functions correctly, a faulty brake booster increases your risk on the road and puts everyone else in danger.

Your best options are to have your car towed to the workshop for a brake booster repair or replacement or have the mechanic visit your location.

Brake boosters typically last throughout the vehicle’s lifespan. Still, there’s always a chance that repairs or replacements are necessary. 

If that happens, you can check out CarpartAU’s Directory to find local automotive workshops that can help you get your brake boosters fixed quickly.


By Ray Hasbollah

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