9 Bad Brake Booster Symptoms (& Replacement Cost)

Did you ever wonder how much brake pressure is needed to bring a 4000 lb vehicle to a halt? It would be impossible to stop such a vehicle on your own due to the amount of pressure. However, you can stop a moving car by pressing down on the brake pedal.

So the question is, how can this be possible? The brake booster is what makes this possible.

Would you like to learn more about brake boosters?

This article will provide detailed information about all you need to know about brake boosters. Its information highlights include what brake boosters are, their functions, the symptoms of a failing brake booster, brake booster replacement, and more.

Let’s get started!

Different brake boosters, including hydraulic boosters, utilize fluid pressure generated by the power steering pump.

The most commonly used brake booster, however, makes use of an Engine Vacuum, and you can also find electric brake boosters in some vehicles.

Related: Squeaking Noise While Driving but Not Brakes Applied

Bad Brake Booster Symptoms

Bad Brake Booster Symptoms

Over time, brake boosters can become faulty and must be repaired immediately to avoid further consequences or damage. The following are some common symptoms of a bad brake booster.

1. A Stiff Brake Pedal

A hard brake pedal is one of the top indicators of a faulty or failing brake booster.

If the brake booster fails, it loses the ability to amplify the force applied on the brake pedal by your foot, and this might require you to use more effort while applying the brake.

Stiff brake pedals reduce the force sent to the master cylinder, thereby decreasing the hydraulic pressure in the brake fluid, which leads to difficulty in braking.

2. High Brake Pedal Position

If you observe that the brake pedal takes more time than usual to return to its original position after letting go or traveling less than expected, the brake booster might have a problem.

3. Hissing Noise From the Brakes

When you brake your car, you might hear a hissing sound if there is a leak in the vacuum hose or your vacuum booster leaks through the diaphragm.

4. Longer Braking Distances

Another indicator of a faulty brake booster is increased braking distance. If you notice that your vehicles take more time than usual to halt after applying the brake, you need to examine the brake booster immediately.

5. Engine Performance Issues

Engine performance issues are another notable symptom of a faulty brake booster caused by a vacuum leak.

This implies that the vacuum check valve is malfunctioning and drawing air into the system, or there might be a hole in the housing or diaphragm of your car.

The air intake from the malfunctioning vacuum check valve might affect the fuel mix in the engine.

6. Fluid Leaks

The leakage of fluid in the vehicle indicates different kinds of problems.

For example, if a vehicle using hydraulic boosters is experiencing a power steering fluid leak, this might mean that the hydro-boost assembly is liable to fail.

An Electronic brake booster can also develop leaks that can affect its efficiency and performance if housed with the master cylinder.

7. Overheated Hydro-Booster

Environmental conditions can sometimes cause the fluid temperature in your hydro-booster to rise.

Temperature jumps can damage your hydro-booster’s seals and spool valve, compromising brake performance.

8. Illuminated Warning Lights

This is basically for cars with the electronic brake booster. The failure of the brake booster can affect the anti-lock braking system (ABS) of cars whose brake booster is electronic.

This will lead to brake warning lights such as the ABS, traction control, or stability control lights.

9. The Power Steering System Fails

One of the functions of the power steering pump is to power the Hydraulic brake boosters. Therefore, if there is a problem with the power steering, this will affect the Hydraulic boosters.

You should take your vehicle to a mechanic as soon as possible if you notice any of the above problems.

Also Read: Can You Drive Without Power Steering?

The replacement cost is highly influenced by the vehicle’s model or make and the mechanic’s labor rate.

Brake Booster Repair and Brake Booster Replacement.

Brake Booster Replacement

A brake booster can be replaced or repaired using essential tools and equipment. The tools and equipment include:

  1. Different sizes of wrenches
  2. Screwdrivers, and
  3. New check valve
  4. New Brake Booster

Follow the step below to replace or repair the brake booster if you have gotten these tools.

Step 1: Initial Verification Checks

To carry out a verification check on a brake booster:

  1. Switch off the engine, then Completely remove all the fluid in the system by pumping the brake pedal until this is achieved.
  2. Start the engine while holding the brake pedal down.
  3. After starting the engine, keep the pedal slightly compressed.

When you have done this, a fluid refill should be confirmed, which is only possible if your vacuum system is in good working condition.

However, if the refill is not successful, examine the hose and replace it if it is bad. On the other hand, if the brake hose is in good shape, you might have a problem with your vacuum system.

You might need to replace your brake booster immediately, as this implies that it is out of order.

Nevertheless, before completely replacing the entire brake booster, first examine the check valve.

Step 2: Check Valve Replacement

  1.  Search for the exact location where the vacuum line is connected to the brake booster. This is where you might find the check valve.
  2. Locate the clamps that hold the valve line and the check valve together.
  3. Remove the clamps so you can easily take out the valve line
  4. Now, take out the check valve with the help of a screwdriver or wrench.
  5. After that, you can now install the check valve in its appropriate location in the brake booster and then replace the vacuum hose.

Restart the car’s engine and check if the brake pressure has been restored. If it has been restored, you are done, but if not, you might need to go ahead and replace the booster.

Step 3: Brake Booster Replacement

  1. First, locate and identify the brake booster behind the brake master cylinder firewall.
  2. Identify clamps on the brake booster
  3. Remove the clamps and take out the vacuum line
  4. Detach the brake booster from the master cylinder by using the appropriate wrenches to loosen the bolts
  5. Loosen and remove any bolt restraining the brake pedal so that the damaged booster will be completely free.
  6. Place the new brake booster in its position behind the master cylinder firewall.
  7. Reinstall and tighten the initial loosened bolts to secure the newly installed booster.
  8. Reinstall the rubber hose back to the fitting.
  9. Connect the vacuum line to the newly installed booster.

Step 4: Safety Tips and Final Checks

The brake lines can get damaged while detaching the faulty booster from the master cylinder.

This is possible because the brake lines are connected directly to the master cylinder. The best way to prevent this is to avoid applying pressure on the brake line while attempting to detach the booster from the master cylinder.

Additionally, do not forget to protect your eyes and body with appropriate clothing.

Check out this video for more tips on brake booster replacement

Frequently Asked Questions About Brake Booster

What Does a Brake Booster Do on a Car?

As the name implies, a brake booster, also called ‘vacuum booster’ or ‘brake servo,’ is a device that helps boost the car’s brake performance. The brake booster makes braking easier for the driver by amplifying the force exerted on the foot pedal.

Does Every Car Have a Brake Booster?

Brake boosters are an integral part of power brake systems, which you can find in almost all vehicles. It magnifies the force applied on the brake pedal by the driver. If the brake booster becomes faulty, the driver will apply excessive force to achieve adequate braking.

Can a Brake Booster Cause Brakes to Lock Up?

If the brake pedal gets stuck in its boost mode, the booster will keep applying force to the brake even after the driver has released the pedal. Quickly stop the car and connect the vacuum hose if your brakes lock up.

Can You Drive With a Faulty Brake Booster?

One of the significant indicators of a failed booster is extreme difficulty in pushing the brake pedal. You must get the brake booster repaired or replaced immediately you discover it is faulty. Driving with a faulty brake booster is dangerous.

How Much Does a Brake Booster Cost?

Replacing a bad brake booster costs between $350 and $1250 for many modern cars. Labor costs range between $100 to $200, and purchasing new parts for the replacement can be as high as $900 or as low as $100.

What Causes a Brake Booster to Go Bad?

One of the major causes of brake booster failure is insufficient vacuum pressure, which happens due to a cracked or loose hose that allows air to enter the system.

Can a Brake Booster Be Repaired?

You can repair the brake booster of any car to perfect working condition. You can do this with a complete brake booster repair kit that features a replacement booster, nuts, bolts, mounting hardware, seals, etc.

How Often Do Brake Boosters Need to Be Replaced?

The brake booster of any vehicle is expected to last from 150,000 miles to the vehicle’s lifetime. However, in a dry climate, the internal diaphragm of the booster can deteriorate due to dry rot and may need to be replaced.

How Do I Know if My Brake Booster Has a Vacuum Leak?

A sign that your brake booster has a vacuum leak is that the brake pedal feels hard immediately after one brake application. Quickly examine the hose of the booster to check for cracks, kinks, or other damages.

Is a Brake Booster Necessary?

The brake booster is quite similar to the power steering. This is a typical power assist system, and the power brakes can work even if the booster fails. Therefore, the brake booster is not necessary.

Is It Hard to Replace a Brake Booster?

Replacement of the brake is not a difficult task. If you can bleed your brakes and Change the brake pads, you can change the booster.

Do You Need to Bleed Brakes After Replacing the Brake Booster?

Yes, you will have to bleed the brakes after replacing the brake booster. However, if you did not open the hydraulic brake lines, you can return the booster without bleeding the brakes. You will need to remove the nut holding the master cylinder to the booster to do this. Then, carefully Separate the booster and the master cylinder without damaging the hydraulic lines.

How Long Does It Take To Replace the Brake Booster and Master Cylinder?

Replacing a faulty brake booster takes an average of 1 to 2 hours, depending on the mechanic’s skill level.

What Happens if You Don’t Replace the Brake Booster?

If you do not replace the booster when the diaphragm inside it becomes bad, the brakes will absorb too much air coming from the engine. This will make your car stall whenever you push your brake pedal. You will face further problems if you continue to drive with this problem.


As the name implies, a brake booster is a device that helps boost the car’s brake performance. It makes braking easier for the driver by amplifying the force exerted on the foot pedal.

The brake booster is an essential component of your car’s braking system. Therefore, you always need to make sure it is in good working condition.

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