How Can I Tell If My Brake Booster Is Going Bad?

Your brakes are an integral part of driving a car which is why it’s important that they work properly.  Not being able to brake or bring your car to a stop when needed can result in you slamming into the car in front of you or sliding off the road into a ditch.  Your car’s brake booster is designed to assist you in bringing your car to a stop by making pressing the brake pedal easier.

So how can you tell if your brake booster is going bad?  One indicator that your brake booster is failing is that your brake pedal is hard to press down.  Another sign that your brake booster is failing is that your engine stalls when pressing on your brake pedal.

But what can you do if your brake booster is failing?  Is it illegal to drive without a functioning brake booster?  Keep reading to find out.

What Does A Brake Booster Do?

Your brake booster is designed to pull air out of the vacuum system coming from your engine to provide additional braking power and make bringing your car to a stop easier.  Without a brake booster, your car would still be able to stop but it would take more force applied by the driver to the brake pedal in order to slow the car down.

What Are The Symptoms Of A Bad Brake Booster?

1. Hard Brake Pedal

One way that you can tell that your brake booster is failing or going bad is that the brake pedal becomes harder to press down.  Your brake booster is designed to allow you to softly press your brake pedal and allow you to easily bring your car to a stop.

When your brake booster is failing it will take more pressure on the brake pedal because the booster can’t properly assist you in applying brake pressure.  Once your brake booster begins to fail it will be up to the hydraulic system of your car to bring your car to a stop.

2. Engine Stalls When Braking

Another sign that your brake booster is failing or going bad is that your car stalls when you apply the brakes.  The brake booster will draw a vacuum from the engine to allow it to provide pressure to the brake system.  As a brake booster fails it can allow the excess vacuum to enter from the engine which can cause the engine to stall out.

If your engine stalls when braking you’d want to check the vacuum and air intake to make sure that everything is working properly.

3. Longer Stopping Distance

One sign that there is something wrong with your brake booster is longer stopping distances.  Like I mentioned earlier your brake booster is designed to assist you in bringing your car to a stop.  If your brake booster is not working properly it can result in longer stopping distances as it won’t be able to help you slow down the car.

If you notice that your brakes aren’t working as they used to and it’s taking you a long time to bring your car to a stop it could be that your brake booster is failing and needs to be replaced.

4. Spongy Brake Pedal

After driving a car for a while, you will get a feel for the brake pedal and how easily it needs to be pressed to allow you to come to a smooth stop without needing to slam on your brakes.  If you start to experience a spongy brake pedal this can be an indicator that there is something wrong with your brake system.

Typically, a spongy brake pedal means that there is air in the lines of your brake system that needs to be removed.  If you’ve just had work done on your brake system, it’s likely that air bubbles have found their way into your brake lines.

The only way to remove air bubbles in brake lines is to bleed the brakes to allow the air bubbles to escape.  At that point, the brake pedal should work like normal again.  If it doesn’t you may have another issue.

Another reason why your brakes may feel spongy is that your brake booster is failing.  Your brake booster is designed to pull air out of the vacuum system coming from your engine to provide additional braking power and make bringing your car to a stop easier.

The problem is that brake boosters, if not working properly, won’t be able to assist you with bringing your car to a stop.

Can You Drive Without a Brake Booster?

While you can drive without a brake booster it may be unsafe to do so.  Brake boosters weren’t that common until the 1950s which meant that plenty of people were driving without brake boosters before the 1960s.

Since the 1960’s cars have become increasingly more powerful which is why brake boosters are needed more nowadays.  Driving without a brake booster will make your car more difficult to stop but it’s not illegal.

Just understand that braking will be more difficult without a functioning brake booster and braking distance will be affected.  So, make sure that you give yourself plenty of distance to stop if you plan on driving without a working brake booster.

While you won’t get a ticket for driving without a brake booster if you live in a state with vehicle inspections your vehicle can fail the inspection if your brake booster is not working properly.  Your brake system is one of the checks when your vehicle is inspected, so expect to fail your inspection if you live in a state that has periodic vehicle inspections.

How Do You Test a Brake Booster?

1. With your car’s engine off press the brake pedal a few times to deplete the stored vacuum in the brake booster.
2. Start your car with your foot on the brake pedal and monitor the brake pedal position.  It should fall to the floor about a quarter inch but then become firm.

If your brake pedal does nothing or presses up against your foot when you start your engine this is a sign that there is something wrong with your brake booster and it likely needs to be replaced.

If you are a more visual learner and would like to check out a Youtube video on how to test your brake booster check out the video below:

What Causes a Brake Booster to Fail?

Brake boosters use the vacuum from the car’s engine to function.  Over time the vacuum lines running from the engine can become old and brittle which can lead to cracks in the vacuum lines.  Cracks in the vacuum lines will allow outside air to enter the brake booster which won’t allow the brake booster to operate properly.

Another reason for a brake booster to fail is that the ports that allow air to escape can become plugged with debris.  When this happens the brake booster can’t allow air to escape properly which can also cause your brake booster to fail prematurely.

Is There a Problem with Your Brake Master Cylinder?

Problems with how your brake pedal feels can also indicate that there is something wrong with your brake master cylinder.  Your brake booster and brake master cylinder work in tandem to help bring your car to a stop.

Modern cars will come equipped with sensors within the brake master cylinder that can detect problems with the brake fluid pressure and brake fluid levels.  That way if your brake fluid gets low it can warn you by illuminating a check engine light or warning you of low brake fluid levels.

If you see a check engine light and your brakes haven’t been operating normally, I’d have the check engine light investigated as it may be pointing to an issue with the brake master cylinder.

Another common issue that can occur with the brake master cylinder is that the internal seals can wear down over time allowing your brake fluid to become contaminated.  Inspecting your brake fluid will reveal if there is a problem with the brake master cylinder seals.  Your brake fluid should be clear.

If your brake fluid has a black or brown tint this is a sign that your brake master cylinder has a leak and needs to be repaired or replaced.

Related Questions:

What Happens If Your Brake Booster Stops While Driving? If your brake booster stops working while driving, you will still be able to stop your vehicle it will just take more effort on your part.

This sort of problem was highlighted in the GM ignition switch issues in the early 2000s where the ignition could be accidentally switched off by their knee.  At that point, the brake booster and power steering would become inactive.

This meant that braking distance would be compromised, and steering would become much harder until the engine can be turned back on.  As you can imagine this leads to a lot of crashes some of which lead to deaths.  As a result, GM was sued and had to pay a large sum of money to the people that were affected.