Quick Tips on Spongy Brakes
- Spongy brakes are primarily caused by air in the hydraulic system, which prevents effective force transfer when braking.
- Immediate attention to brake issues is essential. Faulty brakes put your safety and others at risk.
- Multiple factors can cause spongy brakes, including air in the brake lines, leaking brake lines, low brake fluid, and various component failures.
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 another 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. Faulty brakes can put your well-being and the safety of others at risk. 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?
- Spongy Brakes Symptoms
- Causes of Spongy Brakes
- How to Fix Spongy Brakes
- Bottom Line on Spongy Brakes
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 on the pedal in a familiar car. If you’re a newer driver or in an unfamiliar car, always pay attention to how far you have to push down 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: The need to repeatedly push or pump the pedal to stop the car indicates a brake problem. Safe braking systems engage the first time you push down and do not feel spongy or soft.
- Dashboard brake light turns on: 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.
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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 ASE-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, fluid transfers from the brake cylinder to the brake on each wheel. The fluid creates the hydraulic pressure required to slow and stop the car. A fluid leak compromises the hydraulic pressure. Damage to the brake line or rust in the system can 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 Calipers
Brake calipers squeeze the brake pads against the rotor, creating friction against the wheel and slowing the vehicle. Aggressive driving and braking habits can sometimes damage your calipers. Corrosion, moisture, and debris can also cause issues. Faulty or worn-down brake calipers can sometimes make your brakes feel spongy.
Worn Master Cylinder
In an antilock braking system (ABS), the master cylinder converts the force you apply to the brake pedal into hydraulic pressure, which is transmitted to the caliper through the brake lines. 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 misalignment 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 antilock 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.
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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 by checking for leaks, worn pads, or damaged calipers, rotors, or cylinders. 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.
Preventive Maintenance Tips
Taking care of your brakes is an essential part of car ownership.
- Regular inspection: Check brake pads, rotors, and fluid levels during routine maintenance or tire rotations.
- Smooth driving: Maintain a safe following distance to avoid aggressive braking and reduce wear on braking system components.
- Quality components: Use high-quality brake pads for better performance.
Bottom Line on Spongy Brakes
Spongy brakes, indicated by a soft or squishy feeling when pressing the brake pedal, can arise from issues such as low brake fluid, air in the brake lines, or problems with various components in the braking system. Addressing spongy brakes starts with changing the brake fluid, but a qualified mechanic should diagnose recurring issues. Follow the manufacturer’s recommended maintenance schedule for regular brake fluid changes to prevent corrosion and maintain optimal brake performance.
Editor’s Note: This article has been updated since its initial publication. Chantel Wakefield contributed to the report.
