WHAT THE HECK IS A…Brake Booster?

To know what the heck a brake booster IS, we must first explore what the heck a brake booster IS NOT. A brake booster is not: 

  1. A young cheerleader with a fractured leg
  2. The seat on which a small child can sit to stop a car
  3. A shot administered by a doctor to protect against the Brake-a-noma Virus
  4. The answer to my security question for my online bank account login

That doesn’t look pleasant. At least it’s not one of those shots you get on your bum.

So…what the heck is it then? 

A brake booster is a device that gives the brake pedal some added force when you press it. It’s only part of a disc braking system, which is the current standard—not a drum braking system.

How Does It Work?

The brake booster has two compartments inside it. Both compartments are in a partial vacuum when the engine is on. As the brake pedal is pressed, a valve inside the booster opens, which allows air into one of the compartments, which changes the pressure inside it. The change in pressure helps to push the piston inside the master cylinder forward which sends brake fluid to the calipers, which slows and stops the vehicle.

When the engine is off, the brake booster compartments have no vacuum, so the brake booster does nothing and the brake pedal is hard.


All braking systems use high fluid pressures to slow and stop a moving vehicle. Most people would find it very difficult to press a brake pedal without the help of a functioning brake booster. If the brake pedal is hard, difficult to press, or it seems to take longer to stop the vehicle, there is a possibility that the brake booster is bad. This is a safety hazard because the ability to slow and stop a moving vehicle would then be based on each individual’s physical strength. Believe it or not, not everyone is in peak physical shape (a.k.a. yours truly).

Arnold wouldn’t have any trouble without a brake booster…


So, there you have it. Now you know what the heck a brake booster is NOT, what it IS, and you have most likely compared yourself to Arnold Schwarzenegger and silently wept. If so, I just want to say that it’s going to be okay–you are a unique individual and you are loved!


Tell me what other automotive parts baffle you. I’ll tell you what the heck they are!

Written by Ben Scharff

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