Service Brake Booster Message: Causes and Fixes

The brake booster is a critical component of a vehicle. But what if it fails to respond, causing increased pedal effort? Your brake pedals will feel spongy or stiff. You might experience a longer stopping distance. Let’s go back to the basis to ask, ‘what causes the service brake booster message to appear in the dashboard and what remedy should you watch for? I’ve offered all you need to know about the causes and fixes of a failing power brake booster. Stay connected.

What Causes Brake Booster Failure

I’ll talk about the vacuum brake booster, the most common type. This gas-powered booster uses the engine vacuum to reinforce the pressure you put on the brake pedal. Most of the reasons your power brake booster will break are vacuum-related.

Here are the reasons your brake booster will fail.

Vacuum Leak

The majority of the time, a vacuum leak causes your vacuum brake booster to fail. A leak can happen in a wide range of places. The brake booster can leak; the leak could also come from the engine vacuum. The hose that links the intake manifold can also leak, causing

Hardened Internal Diaphragm

The internal manifold hose can become hard and brittle causing the brake booster to fail. The hose connects the booster to the internal manifold and once it hardens, the booster also stiffens. This way, the pedal won’t firm up, leading to a brake failure.

Low vacuum pressure

A brake booster needs sufficient pressure to maintain the proper pressure your car engine needs to work. However, a low vacuum could increase the chances of the brake booster failing. 

Failed check valve or grommet at the booster

The booster check valve hardly will need maintenance during the lifespan of the booster. This is primarily due to its location. But when you’re repairing the booster, this component may fail, thus causing the booster itself to break

Incorrect Vacuum Hose

The vacuum hose installed in your car may be incorrect or have been disconnected. An incorrect hose will bring out incorrect pressure readings from the engine. If it’s not the appropriate one, simply replace it. For a disconnected vacuum hose, however, you’ll need to reconnect it.

How to Fix Bad Brake Booster 

There are three steps to fixing a broken power brake booster

Step 1: Test if the Brake booster is Fine

You can carry out a simple diagnostic test on your brake booster to know if your car’s vacuum brake booster is in good condition.

  • Switch off the engine
  • Allow it to cool for some minutes (not less than 30).
  • Step on the brake and pump the pedal about 10 times to remove any vacuum air left in the booster.
  • Apply light pressure to the brake pedal before starting the car.

Observe the response of the pedal. If it’s slightly soft on your foot before firming up, note your brake booster is working fine. However, if the pedal is stiff, then there’s a problem with the brake booster.

Step 2: Look for Error Code

The second thing to do is to watch out for the error code. Failing power brake boosters on most modern vehicles typically show an error code. The pressure sensor circuit monitors how much vacuum pressure your foot applies on the brake booster through the pedal. A problem with the brake booster pressure circuit returns with the error code P0556. The ECU or powertrain also detects the P0557, P0558, and P0559 error codes.

Step 3: Replace a Bad Brake Booster

If your car’s power brake booster isn’t working, the thing to do is to replace it. Aside from that, it’s not easy to repair, I’ll strongly advise that you replace the entire failing brake booster. It’s the best idea. Nonetheless, be sure you’ve read the owner’s manual if you’re doing a DIY replacement. The good thing is that you may not need to drain the brake fluid.

A step-by-step guide to replacing a defective brake booster:

Step 1: Check beneath your car windshield for the brake booster

Step 2: Unplug all engine parts, including plastic seals, vacuum hoses, air filter, and other components and accessories that obstruct access to the booster.

Step 3: Pull off the vacuum hose from the booster. Note that this hose may not be removable or visible in some car models.

Step 4: Free the master cylinder, but first relocate the brake fluid reservoir.

Step 5: If you can’t handle Step 4 above well, you may need to drain the brake fluid system.

Step 6: Take off the brake booster once you are able to access it. Follow your vehicle’s manual for instructions.

Step 7: Install the new brake booster replacement.

Step 8: Allow the brake booster to settle and then carry out testing by driving your car around for a few distances. 


How long does a brake booster last?

It depends on a couple of factors, including your driving habits and the quality of the car’s braking system. Besides, the driving conditions and model of the car also count. Nonetheless, on average, a vacuum brake power booster can last 150,000 miles. Some can last the entire lifetime of your vehicle. Vacuum boosters built with stronger and more durable hydraulic pressure boast longer mileage.

How much does it cost to service a brake booster?

The average cost of replacing a brake booster is in the neighborhood of $200 and $800, with labor cost being between $150-$250 while vehicle parts can go for as high $200 to $1000.

How Can I diagnose the engine vacuum?

You can diagnose a problem with the brake booster by doing the following:

  • Locate the brake booster
  • Disconnect the vacuum hose from the engine
  • Plug the inlet into the intake manifold to seal off the engine vacuum side of the hose (make sure you use the right cap s cover)
  • Switch on the engine and allow it to idle for a few minutes.

Note: if the engine idles normally, then the engine vacuum is in good condition. The problem may be a vacuum leak. 

Final Thoughts

There’s a great deal of danger involved in driving around with a faulty service brake booster. You risk personal safety and could cause a fatal accident or death to other road users. To prevent this, it’s vital that you fix the brake boost once you notice it’s failing. I hope this article equips you with enough information to service your brake booster once it gets bad. Have a safe trip.