Skip to content

How Does A Brake Booster Work?

Brake booster from a 1990 Geo Storm GSi.

Bringing your vehicle to a safe stop begins with applying your foot to the brake pedal. That action sets in motion a chain of events where a joined bar thrusts a piston into the master cylinder, which is filled with hydraulic fluid, and the fluid immediately travels through pipes to cylinders located adjacent to each wheel’s brakes.

Within that system is a brake booster, a device tasked with multiplying the force the driver applies when they engage the brake pedal. Here, we’ll talk about the three different types of brake boosters found in modern vehicles.

Brake Boosters and Your Vehicle

You might not know which type of brake booster is utilized in your vehicle, but each one has something in common: they multiply your foot’s pressure on the pedal by two to three times to bring your vehicle to a rapid and safe stop. However, if the brake booster fails, you’ll have to supply all the pressure, and that’s no easy task.

Vacuum Boosters

A quick move from gas pedal to brake pedal will stop your car.The most common type of braking system involves vacuum boosters. These systems utilize a vacuum diaphragm bracketed to a vacuum port found on the engine’s intake manifold. Vacuum boosters are typically utilized with ordinary power brakes, but they can also be found in non-integral anti-lock brake systems (ABS).

Although vacuum boosters are employed in most vehicles, they can function in different ways, depending on the engine. For instance, in gasoline-powered cars, air pressure from the intake manifold helps stop the vehicle. Diesel-powered vehicles with vacuum booster systems, on the other hand, require an auxiliary vacuum pump due to their different parts and functionality.


A hydro-boost system utilizes hydraulic pressure derived from the power steering pump to multiply braking power. This system may be found in vehicles with or without an ABS.

Launched in the 1970s in response to increased fuel efficiency and safety concerns, hydro-boost systems are also known as the “non-vacuum” booster. Whereas the brake hoses are an integral part of the vacuum boost system, the power steering hoses are critical to the hydro-boost system.

A key benefit of this type of system is that if the power steering pump fails, there is typically enough pressure remaining to fully stop the vehicle one to three times.


As the newest braking design available, we’ll hear increasingly more about electro-hydraulic brakes. These are found in integral anti-lock brake systems, particularly in electric vehicles, including some hybrid models. They’re also used in vehicles with “brake-by-wire” systems, in which input from the brake pedal sensor activates the brake booster to apply the brakes. In other words, the physical connection between the gas pedal and the braking system is eliminated and replaced with computer input. Fewer mechanical parts can mean increased reliability.

The Electro-Hydraulic brakes have another benefit that makes them appealing: compatibility with regenerative systems. Such systems slow a moving vehicle by harnessing its kinetic energy, which is converted to electricity and sent to the battery. Recapturing this energy can extend the vehicle’s battery-driven range. In some models, this tech is used to enable one-pedal driving. When a car is operating in this efficient mode, simply releasing the accelerator pedal gradually brings the vehicle to a full stop. Consequently, the brake pads and rotors last longer

Understanding your brake booster type is important, especially when it comes time for repairs. Even if replacing or repairing these systems isn’t something you plan to take on yourself, it’s always best to have an idea of how they work so you can know whether your vehicle is safe to use and keep your mechanic honest.

Check out all the brake system parts available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on braking systems, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.


Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

Leave a Reply

Your email address will not be published. Required fields are marked *