Symptoms of a Bad Brake Booster

The brake booster is equipped with several parts that enable a driver to bring a car to a halt. These components work together and if any of them fails, the entire brake booster will be affected.

The role of the brake booster is to make it easier for a driver to apply the brakes, by applying force to the master cylinder instead, to circulate pressurized fluid that helps in activating the brakes.

The brake booster plays a pivotal role in applying brakes to a car evenly and its failure will cause several problems for the car. Being conversant with the symptoms of a faulty component in your vehicle will enable you to fix it before it gets complicated and expensive. Also, it will prevent accidents and discomfort while driving. If you notice that your brake booster is failing, it is important to swiftly visit an auto repair shop.

This article will examine the various symptoms of a bad brake booster and other things you need to know about your car’s brake booster.

What is a Brake Booster and What Does it Do?

The brake booster is a component that increases the force applied on the brake pedal when such force is being transferred to the brake master cylinder. It reduces the effort of a driver to apply brakes by allowing the master cylinder to distribute pressurized fluid to activate the brakes.

It is a mechanical component of your car that makes it easy to apply the brakes by drawing air from the vacuum system in the engine to enhance the ability to brake your vehicle.

There is usually a need to increase the braking power/force to promptly stop a moving vehicle. The force applied by the driver is not enough on many occasions, which is why a brake booster is employed to effectively increase the force for effective braking.

Also, the brake booster has proven very helpful when driving at high speeds, with heavy or loaded vehicles and in cases of panic braking. During this period, a vehicle requires a very high braking power to be able to decelerate or halt the vehicle and the brake booster provides this additional force.

Brake boosters are of different types, but they serve the same purpose. Some common types include vacuum operated, hydro-boost, and electronic assemblies brake boosters.

Working Principle of the Brake Booster

The working principle of the brake booster is determined by the principles of vacuum pressure in the braking system. The booster is located in the engine region of your vehicle, mounted between the firewall and the brake master cylinder.

A chamber in the brake booster is divided by a diaphragm and is connected to the intake manifold. The brake pedal is then linked to a side of the brake booster while the brake master cylinder occupies the other part.

When a driver steps on the brake pedal, a plunger is pushed down the master cylinder. This allows the brake master cylinder to pass hydraulic fluid from the hoses to the brakes for each car wheel. The hydraulic fluid pressure turns on the master cylinder piston in each brake caliper and creates friction by clamping the brake pads on the rotor to decelerate or halt your vehicle.

The pressure on the brake pedal is the major determinant of how much force the brake booster generates. If the pedal is pressed hard, more pressurized fluid is forced through the system to generate more braking force.

When the brake pedal is stepped on, the shaft opens a valve behind the brake booster chamber and air enters and fills up half of the chamber leaving the other half empty. This process pushes the shaft more on the master cylinder pushrod to create the pressure needed to make braking easy.

Causes of Brake Booster Failure

Here are the most common factors that can lead to brake booster failure in your car.

Engine vacuum and diaphragm leak

A leak in the engine vacuum, brake booster, or the hoses that connect the intake manifold to the brake booster will lead to the failure of the component. The hoses or internal diaphragm of the brake booster can become dry and crack leading to leakages.

Insufficient engine vacuum pressure

This is usually caused by a loose or cracked vacuum hose. Too much air might get into the vacuum and will not let it reach the required vacuum pressure to make the brake booster function optimally.

Damaged check valve or ports

The spring that controls the opening and closing of the check valve can get damaged after a while and will leave the valve stuck open or close. When this happens, the brake booster will malfunction because too much or too little air is entering the chamber.

Wrongly adjusted brake pushrod

The pushrod, also known as the brake booster pin, creates pressure to make braking easy by extending a piston into the master cylinder. If the component is not properly adjusted, it can cause your brake pedal to go in unnecessarily or too short when you press the pedal.

Symptoms of a Bad Brake Booster

When the brake booster is faulty, it will affect the braking system and display some noticeable symptoms. Most common symptoms include:

Stalling engine

When excessive air enters the brake booster chamber due to a damaged diaphragm, broken seals, or cracked gaskets, it will cause your engine to stall when you engage the brake pedal. Ignoring this issue can lead to transmission issues which will become more dangerous, complex, and expensive to fix.

Anti-lock braking system light beams

The ABS sensors will send signals to the engine control (ECU) unit about a problem with the brake booster which will cause the ECU to trigger the ABS warning light on the dashboard.

Increased stopping distance

A vehicle is supposed to stop completely shortly when you engage the brake pedal.

However, if your brake booster is failing, you will have to exert more pressure to make the car to stop completely. This is mostly caused by the presence of excess air in the chamber and can lead to accidents on the road.

Stiff brake pedal

The most common symptom of a failing brake booster is the brake pedal becoming stiff. As stated earlier, the brake booster reduces the effort of the driver to apply brakes, making the process very easy.

However, when the booster is failing, there is nothing to amplify the pressure from the driver’s foot. This means that you’ll have to exert more pressure to get the desired response from your brakes.

Leaking fluid

Hydro-boost brake boosters make use of steering fluid to function effectively unlike their vacuum-operated counterpart. Any crack in the component can cause the fluid to leak which will affect the performance of the brake booster.

Poor engine performance

A faulty brake booster can affect the overall performance of your engine. It can cause the engine to misfire when you start, or stall when you match the brakes.

Hissing sound

This sound emanates from the brake pedal area and occurs when vacuum pressure escapes from the chamber.

When the pressure escapes from the brake booster, it means the component is faulty and will cause a hissing or squealing sound from the brake pedal or under the dashboard.

High pedal position

When the brake booster is failing, your brake pedal will come up instead of remaining at its normal low position. When this happens, you’ll find it difficult to modulate the brakes and might get involved in an accident.

Overheated brake booster

For cars with hydro brake boosters, sometimes, the fluid in the booster can heat up due to certain environmental conditions and make the component extremely hot. When this happens, the seals in the booster can get damaged due to the extreme temperature. Because of the resultant damaged seals, they’d be leakages.

Testing the Brake Booster

If you notice the brake booster is failing, you can confirm this by testing before taking any action.

Here are the procedures for testing the brake booster.

  1. Turn off your engine and depress the brake pedal completely a few times till there is no vacuum anymore in the brake booster.
  2. Press the pedal down again and do not remove your foot this time while you turn on your engine.
  3. If the brake booster is still functional, you will notice a response from the brake pedal as you turn on the engine. Otherwise, there is a problem with the brake booster.
  4. You can go ahead to inspect other components like the booster check valve and vacuum. You can test vacuum pressure by turning off the engine after letting it run for a few minutes then press the pedal slowly and observe as it becomes firmer if the booster is not leaking.

Brake Booster Replacement Cost

The cost for replacing a brake booster is not so cheap and varies according to your car make, model, and where you do the repairs. Usually, replacing this component can cost between $300 to $700. The brake booster cost between $200 and $500 while labor costs between $100 and $200.

Frequently Asked Questions

What is the average life expectancy of the Brake Booster?

The brake booster is designed to last the lifespan of your vehicle. However, some vehicles might come with low-quality brake boosters, and you might be required to replace the brake booster at least after 50,000 or 100,000 miles. The life span of your brake booster also depends on how often you use the vehicle, your driving habits and driving condition.

Can the Brake Booster be repaired?

Yes! The brake booster can be repaired but this should be done strictly by a professional and will also depend on the damage. It will require preliminary checks and replacement or repairs of any damaged part of the booster.

Can I drive without a Brake Booster?

Yes! You can but this is at your own risk. A faulty brake booster will affect braking and cause difficulties in braking. The engine may stall when you try to brake. This is risky and can lead to dangerous situations. Hence, it is not advisable to drive with a faulty brake booster.

How will I know when my Brake Booster is going bad?

When the brake booster is bad, it will cause braking problems in your car. You will experience problems like increased braking distance, engine stalling, brake pedal becoming stiff, and sinking brake pedal. All these and many more will indicate that there’s a problem with your brake booster.

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