Tech Talk with Master Power Brakes

How Does a Brake Booster Go Bad? (Signs of Failure)

Posted by Master Power Brakes Team on Dec 16, 2019 11:36:00 AM

Power brake boosters offer an amazing technology. By using vacuum pressure to your advantage, power brake boosters allow you to stop the car with minimal force on the pedal.

Like all technology, though, brake boosters can fail. Although this is relatively rare, it is important to know just what to watch for in determining if your power brake booster is going bad or has failed. You can then take the right steps to rectify the problem and keep your vehicle in optimal condition for years to come.

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Symptoms of Brake Booster Failure

Power brake boosters use vacuum from the engine, or a standalone pump, to assist in slowing down the vehicle as you depress the brakes. This makes the brake pedal much easier to press down and improves the braking response of the vehicle. Every component must complete its job without fail or the brake booster will not be able to apply the right amount of pressure. When this happens, you might notice the following symptoms.

  • 1. Brake Pedal Hard to Press

When fully operational and everything is correct within the system, the brake booster will make the brake pedal feel much easier to press when applying the brakes in an effort to stop the vehicle. It won’t necessarily make the brakes better which most people think but it will definitely make the car more enjoyable to drive and stop.

When the system stops working right, however, you must apply that additional pressure to the brake pedal to activate the brakes. So, when the booster starts to fail, you will likely notice that the pedal is much harder to push down.

  • 2. Extended Stopping Distance

Without the brake booster’s assistance, the power of your braking system is greatly compromised. As this occurs, you may notice that your vehicle’s stopping distance has increased by several feet or more. This problem is likely to continue to worsen until the brake booster problems are properly addressed.

  • 3. Engine Stalls While Braking

If the seals inside the brake booster have failed, the system may try to pull more vacuum from the engine to compensate. At a certain point, the excess draw will cause the engine to stall out as you depress the brake pedal. With so much vacuum pressure flowing through the system, this can even cause brake fluid to end up inside the booster, as can damage to the seals in the master cylinder.

If you notice any of these problems, it is important to track down the problem and perform all necessary repairs. Driving around with a failing or bad brake booster is quite dangerous, as it can lead to complete brake failure down the road.

RELATED: Carbon Fiber Brake Boosters are Next

How to Fix Power Brake Booster Problems

Fixing a power brake booster generally means replacing the booster. How you go about doing that is based on the booster's design. Some older designs will come apart with common hand tools, but many are put together with a crimped design, making it impossible without special tools and equipment. If the booster is indeed bad and keeping the original is a must, there are services that will rebuild your existing unit; however, replacement is generally the best choice.

The symptoms described above can lead one to think that the brake booster is indeed bad. There are, however, other things that can be causing a brake booster to appear defective.

The fix may be quite simple.

Possible Reasons for Power Brake Booster Failure 

Be sure to check the following when diagnosing the problem:

  • 1. Low vacuum pressure from the engine

  • 2. Failed check valve or grommet at the booster

  • 3. Incorrect or disconnected vacuum hose

An example of a small problem could be the hose. If a fuel hose was used in place of a vacuum line, then the hose could collapse and leave the power brake booster without the pressure it needs to function correctly. How disappointing to go through the replacement of the booster to find out a simple hose could fix the problem. 

Tech Tip: Troubleshoot your problem thoroughly and get a complete understanding of what is causing your brake booster to perform poorly. This will save you time and money. 

By thoroughly troubleshooting and understanding what is compromising the performance of your power brake booster, you can perform just the right repairs and get your car back on the road fast. You will also save money in the long run by pinpointing the exact issue and avoiding the dreaded parts cannon.

Master Power Brakes Expert

Topics: Brake Boosters, Parts

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