Why is my Brake Pedal Spongy? | What are the causes of Soft Brake Pedal?

The vehicle’s brake is one of the most important parts to control it. The brake should feel strong as press it downward. There is something wrong if your brakes seem spongy or soft. This article mainly explains the symptoms and causes of a soft or spongy brake pedal.

What is a Soft Brake Pedal?

A condition in which the brake pedal doesn’t have the necessary hardness is known as a spongy or soft brake pedal. When your car brake pedal becomes soft, you are endangering the safety of your passengers and yourself. There are many factors that may cause a spongy brake pedal.

Soft Brake Pedal

You must feel solid pressure while pressing the brakes of your vehicle. A spongy brake pedal causes the brakes to seem mushy or as if the pressure is fluctuating when you use the brakes. Spongy brakes feel identical to squishy brakes and have the same meaning.

How Does Brake Pedal Work?

The stiffness of the brake pedal is determined by the pressure of brake fluid in the brake lines and master cylinder of your car braking system.

The master cylinder reacts as you push the brake pedal to slow down or stop your vehicle by forcing brake fluids in the brake lines and activating the brake piston. The caliper piston then engages the rotor and apply force to the brake pad.

The pressure on the brake pedal activates the actuator if your vehicle has drum brakes. In order to slow down your vehicle, this forces the shoes outward against the drum’s internal surface.

Causes of Spongy Brakes

The soft or spongy brake pedals are very dangerous for your vehicle. They increase the chances of your vehicle accident. Therefore, you must constantly inspect and maintain your car brakes.

Following are the major causes of soft or spongy brakes:

1) Air In the Brake System

One of the most common causes of spongy brakes is the presence of air in the brakes. As the brake fluid level drops, then air immediately enters the brake line to complete the vacuum.

An air bubble might obstruct the passage of brake fluid and reduces the hydraulic pressure of the vehicle braking system. If your vehicle has a loose bleeder valve, the brake fluid may also gradually absorb moisture.

The mechanic will assist you in flushing the brake system:

  • Remove the moisture that brake fluid absorbs with time.
  • Stop the old brake fluid from boiling, which may lead to a soft pedal.

2) Damaged Brake Lines

The brake lines are one of the most frequently damaged parts of the brake system.  Brake lines, which are typically comprised of steel tubing, may rust from:

  • Wear-and-tear
  • Moisture
  • Road Salt

The damaged brake lines may cause a brake fluid leak, resulting in low hydraulic brake fluid. The low hydraulic brake fluid may have an impact on your pedal travel because brake pedal needs frequent pumping and appropriate fluid to achieve the proper amount of pressure.

3) Old Brake Fluid

While brake fluid might last for a long time, it cannot stay forever. The reality is a little bit more difficult, even though some manufacturers have fix service intervals between 21,000 and 30,000 miles.

This is because, as long as there are no leaks in the braking system, the fluid itself may last for about 100,000 miles. However, as air is entered the system, it begins to oxidize and starts adding moisture to the fluid.

This is bad for your car brake pedal. Your brakes may feel softer as more moisture is added, which is a warning indication that you should flush the system and replace the brake fluid.

5) Low Brake Fluid

Brake fluid has an important role in assisting your vehicle to slow down.

The fluid transfers the applied pressure on the brake into the force which is needed to stop the vehicle.

Low brake fluid will cause your brakes’ hydraulic system to malfunction, resulting your brake pedals sink to the floor.

6) Damaged Master Cylinder

The master cylinder is an important component of braking system of your vehicle.

It stores the brake fluid, produces hydraulic pressure, and distributes it to the front and back brakes. It basically compresses the brake fluid to the place where it is needed to assist your car to stop.

Seals inside the cylinder might crack or leak over time. Furthermore, the master cylinder has responsibility of creating hydraulic pressure, any harm to it might have a significant impact on your braking fluid pressure.

7) Leaking Wheel Cylinder

Some types of latest vehicles have drum brakes on the rear wheels and disc brakes on front.

In a drum braking system, the drum revolves with the wheel. This drum contains a pair of shoes.

The wheel cylinder presses against the pair of brake shoes to slow down the wheel.

Your brake pedal may feel soft as a consequence of rusting in the brake cylinder, which may lead to brake fluid leaks and a loss of hydraulic pressure.

8) ABS Modulator Issues

The Anti-lock Braking System (ABS) modulator contains a hydraulic component installed in ABS-equipped vehicles. It has responsibility to regulate the amount of braking pressure applied to each wheel.

When the ABS modulator goes bad, it leads to the brake valve malfunction which causes of spongy brake pedal.

9) Misaligned Rear Brake Shoes 

Drum brakes are equipped with a self-adjuster that maintains a predetermined distance between the brake shoes and the drum itself. The adjuster sets itself to maintain the minimal distance as the brake shoe lining wears out, which causes the space between the drum and brake shoe to widen.

If your car has a back brake drum and pressing the brake pedal increases your brake pedal feel, your rear brake shoes may not be adjusted properly.

10) Faulty Brake Booster

A faulty brake booster is one of the main causes of soft or spongy brake pedal.

When a brake booster goes bad, it cannot provide you the necessary braking help.

This often occurs when the brake booster is overloaded with fluid, impairing its abilities.

11) Leaking Disc Brake Caliper

Disc brake calipers (the part that presses the brake pad against the rotors to stop or slow the car) may also get corroded with rust, forcing the internal piston seal to leak brake fluid. As the brake caliper leads, the brake pedal may become excessively low or fall to the floor.

Read More: Signs of Low Transmission Fluid

Symptoms of Spongy Brakes

1) Your Brake Pedal Keeps Sinking

If your is not able to maintain braking pressure according to the requirements, the brake pedal will sink and provide no resistance when pressed.

If your brake pedals sink, it is one of the clear symptoms of spongy or soft brakes.  In such condition, you should get it examined as soon as possible.

2) Brake Warning Light illumination

Few vehicles contain a dashboard brake warning light that illuminates as your brake system is damaged.

Your warning light might be alerting you to anything, from an engaged parking brake to a low level of brake fluid in your vehicle.

It might, however, indicate an issue with your brake fluid pressure.

To be safe, get all of your braking components examined anytime the warning light glows.

3) You need to Pump your Pedals

If you are pumping your car brakes continually pump to slow it and to prevent it from moving forward, this might be an indication of a fluid leak in the brake system.

A damaged or leaky master cylinder might be to blame for the absence of a brake warning light and the presence of no apparent leaks of brake fluid. This indicates that your car needs emergency attention.

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