The brake booster is an amazing piece of equipment. It is the reason your 110-pound grandmother can bring a 4,000-pound vehicle to a screeching halt.
Luckily it doesn’t fail often, but will brakes work with a hole in the booster? If there is a hole in your brake booster, the brakes will still function, but you will be unable to press the brake pedal hard enough to brake safely. There is one exception: if the hole is in the front of the control housing, it may not make an appreciable difference.
The extent to which you will be able to apply your brakes in a safe manner depends on the size of the hole. Continue to read for a detailed explanation of how a hole in your brake booster will affect your brake system.
A Hole in the Brake Booster
A hole in any part of the brake booster would make your brake pedal very difficult to press.
The purpose of the brake booster is to increase the amount of force you put into your brake system. Without it, you would feel like you need two feet on the brake pedal to get your car to stop.
To understand why a hole in the brake booster is such a problem, you must first understand how a brake booster works.
To put it as simply as possible, the brake booster uses two vacuum chambers separated by a diaphragm to multiply the force you apply to your brake pedal.
When you press the brake pedal, it causes the vacuum chamber closest to the brake pedal, also call the atmospheric chamber, to fill with air. The pressure between the chamber filled with air and the chamber that is still a vacuum will multiply the force you are exerting on the pedal.
A booster with a 7-inch diaphragm and -8 psi of vacuum would produce over 300 pounds of pressure (Source.) Not bad for something that doesn’t weigh much more than 10 pounds.
When you remove your foot from the pedal, the amount of air and pressure in the atmospheric chamber decreases. A spring resets the vacuum until you apply your brakes again.
If you’re having trouble understanding how a brake booster works, you’re not alone. I found this helpful video that explains it in great detail and in three dimensions.
If there is a hole in either of the chambers, this would cause a vacuum leak. A hole the size of a pinprick may only make a small difference to how your brakes operate, but most holes would render your vehicle unsafe to drive.
Your brake pedal would become exceedingly difficult to push. Can you imagine trying to stop quickly because the person in front of you decided to make a sudden turn when your brake pedal takes two feet to press down?
A broken or malfunctioning brake booster is not safe, and you should not drive the car at all.
There is one exception.
There is always an exception. If the hole is in the front of the control housing, you would be less likely to experience any issues.
The front of the control housing is not airtight, and proper ventilation is actually essential to the workings of the booster.
Of course, if whatever created the hole in the front of the control housing in the first place damaged a vital piece of the brake booster, then the brake booster would likely stop working.
Hydro-Boost
Hydro-boost brake boosters do not use a vacuum system. They are not as commonly found as the vacuum style boosters.
They are smaller and provide more boost than a vacuum brake booster. In addition, hydro-boost brake boosters work with diesel engines. Cars with diesel engines and vacuum brake boosters require a separate vacuum pump.
Hydro-boost boosters use pressure and fluid from the power steering system to multiply the force you put on a brake pedal.
A hole in a hydro-boost brake booster would likely be just as catastrophic as a hole in a vacuum brake booster. The moving parts of a hydro-boost booster fit together with precision. A fluid leak or fluid contamination will cause the booster to malfunction.
Electro-Hydraulic Braking
Electro-hydraulic braking uses a control unit and information from various sensors around the car to determine how much hydraulic pressure to apply to each caliper. Hybrid vehicles often use this braking system.
This system is significantly more advanced than the other brake boosters, but the purpose is still the same – to apply enough pressure to the brakes to bring the car to a safe stop.
A hole in any part of this system would likely result in a malfunction or brake fluid leak. This would make braking impossible. Although many of these systems have built fail safes into their designs so that the car will come to a stop if at all possible when a malfunction occurs.
What Causes a Hole in the Brake Booster?
A hole in the brake booster is not a common occurrence. Brake booster problems more generally occur when a hose becomes faulty or a piece inside the booster breaks down.
A hole could occur if there is a leak of brake fluid between the master cylinder and the brake booster. Brake fluid would eat through the paint of the brake booster and the booster would begin to rust, eventually leading to a hole
An accident, while someone is working on their car, could also occur. In my research, I found a few cases of people hammer/drilling into the booster by accident. A real oops moment.
How to Test Your Brake Booster
If you suspect you are having trouble with your brake booster, hole or otherwise, there is a simple test you can perform to see if it is working.
- Get into your car, and with the engine off, pump the brake pedal six times or so. This will deplete the vacuum stored in the booster, a safety mechanism that allows you to brake if your engine dies suddenly.
- Rest your foot on the brake pedal and apply light pressure.
- Turn the engine on and observe how the brake pedal responds.
- The pedal should move toward the floor if you are applying light pressure. If this happens, whatever issue you are experiencing with your brakes is probably not caused by the booster.
- If nothing happens to the pedal or it pushes back against your foot, there is likely something wrong with the brake booster.
The Cost of Replacing a Vacuum Brake Booster
If there is a hole in your vacuum brake booster, you will have to replace the whole thing. There is no easy or long-lasting way to patch it. Luckily, this is not a common occurrence, and brake boosters often last longer than the cars they are attached to.
The cost of replacing the vacuum brake booster ranges between $539 and $737 for parts and labor (Source).
Common Issues With the Brake Booster
Engine vacuum leak: The engine provides the vacuum for the brake booster. If the hose connecting the engine to the booster becomes damaged, it will cause a vacuum leak.
Diaphragm failure: The diaphragm that separates the two vacuum chambers in the brake booster can harden over time. This will cause internal vacuum leaks.
It can also cause your engine to stall when you apply your breaks because the booster will take too much vacuum from the engine.
Plugged ports: Ports that allow air to leave the booster and enter it. If these ports become plugged, the booster will not do its job well.
Check valve: Sometimes the check valve becomes stuck open or clogged or otherwise fails. Luckily this is an easy fix.
Damaged seal: The seal between the brake booster and the master cylinder can sometimes become damaged. Brake fluid will leak from the master cylinder into the brake booster causing damage.