Why Do My Brakes Feel Spongy?

By Chantel Wakefield 05/17/2023 4:00pm

Quick Tips on Spongy Brakes

  • Malfunctioning brakes are dangerous. Have a qualified mechanic inspect them immediately if you suspect anything is wrong with your car’s brakes.
  • Brakes should feel responsive yet firm when you tap the pedal.
  • A common cause of spongy brakes is air in the brake line.
  • Change brake fluid periodically to help prevent spongy brakes.

Stepping on the brake pedal and feeling it sink to the floor can be quite unnerving for a driver. Yet spongy brakes are a common issue that a range of factors may cause.

All passenger vehicle brake systems use a hydraulic fluid that transfers force through high-pressure brake lines. The softness you may feel is often caused by air inside the hydraulic system. When air or other gas gets into those lines, it compresses when you hit the brakes without effectively transferring force. That will result in a spongy feel at the brake pedal.

Take care of any brake issue immediately because your well-being and the safety of others are at risk with faulty brakes. Below, we’ll examine other factors that can cause your brakes to feel spongy. Keep reading for information on how to diagnose and fix the problem.

What Are Spongy Brakes?

When you engage the brake pedal, it should feel responsive with a bit of resistance. If you tap the pedal and it feels soft, squishy, or mushy, this is a problem. “Spongy” brakes are easy to diagnose for experienced drivers who are used to the firm push of the pedal in a familiar car. If you’re a newer driver or in an unfamiliar car, always pay attention to how far down you have to push before the brakes engage.

Spongy Brakes Symptoms

Here are some common symptoms of spongy brakes:

  • Sinking Pedal: If you tap the pedal and it easily sinks beneath your foot, this is a problem. Healthy brakes are firm and reactive. As soon as you push down, you should feel resistance.
  • Pumping the Pedal: You likely have a spongy brake issue if you must repeatedly push or pump the pedal to stop the car. Safe braking systems are designed to engage the first time you push down.
  • Dashboard Brake Light Turns On: As always, a warning or indicator light on the dashboard signals an issue with the brakes. If your brake light is constantly on or blinking, take the vehicle to a mechanic for brake repair as soon as possible.

Causes of Spongy Brakes

Spongy brakes may be caused by various issues in the braking system. General “wear and tear” is normal over time, but if you’ve recently replaced your brake pads and rotors, there may be a bigger problem. Visit a repair shop for a proper diagnosis from a qualified mechanic.

Air in Brake Line

The most common cause of this is air in the brake line, according to Gary Hardesty, our in-house maintenance expert and A.S.E. certified master technician. “Air can get into the brake lines by a failed seal or through brake pad wear,” Hardesty said. “This causes the brake master reservoir to drop to the point where air can enter the sealed hydraulic system.”

Additionally, brake systems generate a lot of heat at the discs or drums during use. Some of that heat gets transferred into the brake calipers or brake cylinders and up the hydraulic lines. The heat can cause water to vaporize into a gas, resulting in a spongy brake.

Another possible source of gas in the lines is the brake fluid itself. It can actually boil if the brake system gets too hot. One cause of excess heat is a sticky caliper or wheel cylinder that causes the brake pads to drag on the disc or drum continually. Defective springs on rear drum brakes can also cause dragging. A dragging front brake pad will usually cause a car to pull left or right.

Flushing the brake fluid can help clear air from your brake lines.

Leaking Brake Line

The brake line is a crucial part of your car’s brake system. Every time you press the pedal, it transfers fluid from the brake cylinder to the brakes on each wheel. The fluid creates the hydraulic pressure required to slow and stop the car. If there’s a leak, it compromises the amount of pressure applied. Damage to the brake line or rust in the system can both cause a leak.

Low Brake Fluid

A leaking brake line can lead to low brake fluid. Regular driving will also wear down your brake pads and fluid levels. The loss of pressure from the fluid will make your brakes feel soft and spongy over time.

Damaged Disc Brake Cylinder

Disc brake cylinders are also known as brake calipers. They squeeze the brake pads against the rotor. This creates friction against the wheel and slows the vehicle. Aggressive driving and braking habits can sometimes damage your calipers. Collisions, moisture, and debris can also cause issues. Faulty or worn-down brake cylinders can sometimes make your brakes feel spongy.

Worn Master Cylinder

In an anti-lock braking system (ABS), the master cylinder takes the force you apply to the brake pedal and converts it into hydraulic pressure. Brake fluid helps make this possible. If the master cylinder seal is broken or worn, it compromises the amount of pressure applied to the system. As a result, the pedal may feel spongy.

Wheel Cylinder Leak

The wheel cylinder uses pressure to move the brake shoes against the brake drum, which creates friction. Friction slows the vehicle. If the wheel cylinder is leaking, the pedal can feel spongy. Seals inside the wheel cylinder wear out over time and cause leaks, so get them checked each time you have your brakes serviced or replaced.

Rear Brake Shoes Adjustment

If your rear brake shoes are improperly adjusted, they may fail to contact the brake drum properly. This means less force will be applied, causing a spongy feel in the pedal. Accurate rear brake shoe adjustment is essential for maintaining brake performance and preventing premature wear.

ABS System Malfunction

ABS stands for anti-lock braking system. This safety feature is standard in modern vehicles and helps prevent the wheels from locking up when you hit the brakes too hard. It can be especially helpful on slippery or icy roads and surfaces.

The ABS can malfunction and fail for various reasons, including a faulty sensor, a hydraulic leak, or a computer error. A defective ABS can trigger the system to engage more often than it should. This may wear the brake pads down more quickly, making the pedal feel squishy. A malfunctioning ABS can significantly reduce your braking performance, so have it serviced before getting back on the road.

RELATED: Brake Repair: How To Diagnose

How To Fix Spongy Brakes

The first step in addressing spongy brakes is to change the fluid. If the brakes are operating properly now and you’ve had them inspected for safety, delay further repairs unless the condition returns. If it does, you should immediately have a mechanic diagnose the problem. A second opinion may help.

Generally, it is wise to change your brake fluid periodically as part of routine maintenance, even though few manufacturers recommend it. “Brake fluid is very hygroscopic, meaning it attracts water easily,” Hardesty explains. And that can bring problems. Besides causing spongy brakes, water in the brake fluid causes corrosion that can ruin calipers and brake cylinders. Brake fluid changes are relatively inexpensive, so you should have it done every year or two