Understanding brake booster

The brake booster is a part of power braking systems, which are present in almost all automobiles, and it boosts the force that the driver applies to the brake pedal. If the booster malfunctions, it will take a lot of pedal pressure to accomplish adequate braking.

Vacuum servo

The majority of brake boosters depend on the engine’s vacuum to operate. A ruptured diaphragm or a loose vacuum hose are two very straightforward booster failure causes that call for component replacement. Thus, in this article, I’ll be discussing the meaning, functions, diagram, location, types, working, and symptoms of a bad brake booster. You’ll also learn the replacement cost of a brake booster.

Let’s dive in!

Ok then, let’s get down to business.


What is a brake booster?

A brake booster, commonly referred to as a “brake servo” or “vacuum servo,” does just as its name implies: it aids in “boosting” the performance of the brakes. By increasing the force applied without requiring the driver to apply additional force to the foot pedal, a brake booster facilitates braking for the driver.

As you press down on the brake pedal while driving and reach a stop sign, your automobile will begin to slow down. The brake booster supports the brake pedal with more power on the master brake cylinder when you push the pedal by using engine vacuum and pressure. Furthermore, the booster is what distinguishes a car with power steering from one with manual steering. Most frequently, they are utilized with vehicles that have hydraulic brakes as opposed to pressurized air system brake circuits.

Ensuring that the brake pads grip properly and with sufficient force, it helps the entire braking system. There are several different kinds of boosters available today, with the dual-piston master cylinder, vacuum boost brakes, dual-diaphragm vacuum boost brakes, hydro-boost brakes, and electric hydro-boost brakes being the most popular. Depending on the size and year of your vehicle, one of these may be present; nevertheless, the normal vacuum booster is the most traditional design.

Here are some other common names of brake boosters:

  • Power brakes system
  • Brake power booster
  • Vacuum booster
  • Diagram of a brake booster

Working of a brake booster

The brake booster, which is positioned between the brake pedal and the master cylinder, boosts the force of the brake pedal even further. This is accomplished by using the brake booster function to emphasize the force your foot applies to the master cylinder (in petrol-powered autos).

Brake booster

By using a diaphragm system, the booster adds force to the brakes by using a vacuum (and a little air). A small valve in the booster is cracked open when the brake pedal is depressed, allowing air to enter one side of the diaphragm through the lever that connects to the master cylinder.

The pressure on that side of the diaphragm is increased as a result, and the lever is pushed along even further. This pushes the master cylinder piston, and the rest of the process proceeds as usual. That’s basically how it works!

Types of brake booster

Here are the major types of brake boosters:

Vacuum Brake Booster

The one that is most commonly employed is the vacuum brake booster. It increases the force applied to the brake pedal while using naturally aspirated petrol engines.

Vacuum Pump

A vacuum pump may be used in some road vehicles in place of the engine intake manifold. Vehicles with turbocharged engines, diesel-powered vehicles, electric automobiles, and hybrid automobiles commonly use vacuum pump brake boosters.

There are two ways to power vacuum pumps: mechanically (from the engine) or electrically (electric brake booster). In high-altitude areas where naturally aspirated vehicles are unable to generate adequate vacuum for the brake booster, the vacuum pump is also used.

Hydraulic Brake Boosters

Instead of relying on vacuum pressure, this type of brake booster utilizes direct hydraulic pressure produced by the power steering pump.

Location of a brake booster in a car

The vacuum servo, typically known to as a brake booster, is normally found attached to the firewall on the driver’s side of the engine compartment. Additionally, the vacuum source from the engine and the brake master cylinder are both connected to this big, round device.

Location of a vacuum servo

The vacuum servo makes it easier for the driver to apply the brakes by using the vacuum pressure produced by the engine. The vacuum servo multiplies the force the driver applies when the brake pedal is depressed, making it simpler to stop the car.

How do you test a brake booster?

It is crucial to test a brake booster to make sure it is operating properly and giving the brakes enough power support. To test a brake booster, follow these steps:

  1. Start the engine and let it idle for a few minutes to build up vacuum pressure in the brake booster.
  2. Turn off the engine and pump the brake pedal a few times to release any vacuum pressure that may have built up in the brake booster.
  3. Press down firmly on the brake pedal and hold it in place. If the brake pedal is hard to press and doesn’t sink down, the brake booster is likely working properly.
  4. While still holding down the brake pedal, start the engine. The brake pedal should sink down slightly and then become firm as vacuum pressure builds up in the brake booster. If the pedal does not sink down or feels hard, the brake booster may be faulty.
  5. Test the brake pedal feel while driving. Take the vehicle for a test drive and apply the brakes at various speeds. The brake pedal should feel firm and responsive, and the vehicle should stop smoothly. If the brake pedal feels spongy or goes to the floor, the brake booster may not be working correctly.
  6. Examine hissing sounds. Listen for any hissing sounds coming from the brake booster or vacuum lines. A hissing sound could indicate a vacuum leak, which may cause the brake booster to fail.

If you suspect that your brake booster is not functioning correctly, it is important to have it inspected by a qualified mechanic. A faulty brake booster can greatly affect your vehicle’s ability to stop, which can be dangerous in emergency situations.

How much does it cost to replace a brake booster?

Costs for brake booster replacements range from $325 to $1250. Labor costs normally range from $100 to $200, while the price of an automotive part can range from $100 to $900. (or more). The cost is mostly affected by the make and model of your car, as well as the technician’s hourly charge.

Related Article


In conclusion, the brake booster is an essential component of a modern car’s braking system that is made to improve driver safety and braking effectiveness. It lessens the physical effort needed to achieve effective braking, especially in larger and heavier cars, by amplifying the force supplied to the brake pedal.

The brake booster’s importance in maintaining reliable fast braking is made clear by understanding what it does. Maintaining the integrity of this important safety part requires routine maintenance and immediate attention to any indications of failure or reduced effectiveness.

The brake booster ultimately shows the industry’s commitment to improving driver safety and the entire driving experience while serving as a tribute to the ongoing improvements in automotive technology. Its effective operation promotes safer driving conditions and assured stopping ability, two crucial components of responsible vehicle ownership.

That is all for this article, where we discussed the meaning, functions, diagram, location, types, working, and symptoms of a bad brake booster. We also discussed the replacement cost of a brake booster. I hope it was helpful, if so, kindly share it with others. Thanks for reading, see you around!