Spongy Brakes: 9 Reasons for a Soft Brake Pedal + What to Do

Looking for solutions to spongy brakes or a soft brake pedal?

Your brake pedal should have a firm feel when you press down on it.
If it has a soft or a spongy feel, something’s wrong.

And since brakes are a vital part of controlling your vehicle, you should immediately get your vehicle checked to diagnose the issue.

In this article, we’ll discuss the symptoms and causes of a spongy brake pedal. We’ll also explore what you can do about spongy brakes.

Let’s dive in.

How Does Your Brake Pedal Work?

The firmness of your brake pedal results from the brake fluid pressure in your brake system’s master cylinder and brake lines.

The brake line and brake hose form a pipeline from the master cylinder to the brake caliper or wheel cylinder. Brake lines are stiff, but brake hoses are flexible, so they can adjust to your wheel movements.

When you depress your brake pedal to slow or stop your car, the master cylinder responds by pushing brake fluid into the brake lines to activate the brake piston. The caliper piston then closes on the brake rotor and squeezes the brake pad.

If your car uses drum brakes, the brake pedal pressure activates the wheel cylinder. It pushes the shoes outward against the inner surface of the drum to slow your car down.

Essentially, irrespective of which type of brake system you use, the entire process starts with you pressing down on your brake pedal.

What are Spongy Brakes?

In a normally operating brake system, you shouldn’t experience mushy brakes. In fact, you should feel little to no difference in the firmness of the brake pedal during any part of the braking process.

However, several reasons could lead to a spongy or soft pedal.

If you press down on a spongy brake or soft brake, here’s what happens: Instead of all the pressure going to the brake pistons, some of it leaks out.

When releasing the brake pedal, the returning motion sucks in the air, and you experience a spongy or soft brake that goes directly to the floor with minimal resistance.

The 3 Symptoms of Spongy Brakes

Spongy brakes can compromise your vehicle’s performance and, more importantly, compromise your road safety.

Here are a few noticeable things that can warn you of a brake problem, like soft or mushy brakes:

1. Your Brake Pedal Keeps Sinking

If a vehicle can’t hold brake pressure as effectively as it should, it’ll result in your brake pedal sinking with no resistance whenever you press down on it.

If your brake pedal is sinking, it’s a tell-tale sign that your brake system has some issues, and you need to get it inspected as soon as possible.

A short-term solution to slow your car down with such a pedal is to repeatedly pump your brakes since pressing down just once won’t generate enough pressure.

2. Your Brake Warning Lights Are On

Your car will have a built-in dashboard indicator light that lights up when the brake system is compromised.

Your warning light could be notifying you of anything — from an engaged parking brake to the car running low on brake fluid. However, it could also indicate problems with your brake fluid pressure.

To be safe, consider having all your brake components checked whenever the warning light flashes.

3. Your Pedal Requires Pumping to Keep it from Creeping Ahead

If you need to repeatedly pump your brakes to slow your car down, check your brake system for a fluid leak.

If the brake warning light isn’t on and there’s no visible brake fluid leak, you could be dealing with a worn master cylinder, or it may be leaking internally.

It’s a sign that you must take your car to a mechanic immediately and get that brake problem looked at.

9 Common Causes of Spongy Brakes

Your braking systems rely on evenly distributed hydraulic pressure to bring your vehicle to a stop. Any disturbance in the balance of pressure will result in your car needing more time, distance, or effort to stop.

Here’s what could cause these pressure imbalances that lead to spongy brakes:

1. Air in the Brake Line

When the brake fluid is low, air enters the brake line to fill the void.

An air bubble can prevent the brake fluid from flowing properly and compromise the hydraulic pressure of your brake system. Your brake fluid can also absorb moisture over time if your bleeder valve is loose.

Your mechanic will help you flush the brakes (or bleed your brakes) to:

Get rid of the moisture that brake fluids absorb over time
Prevent the old brake fluid from boiling, which can also cause a soft pedal

2. Low Brake Fluid

Brake fluid plays a key role in helping your car slow down.

How?
Brake fluid converts the pressure you apply on the brakes into the force required to bring your car to a stop.

Low brake fluid will disturb the hydraulic system of your brakes and make your brake pedal sink to the floor. That’s why it’s important to top up your brake fluid reservoir with fresh fluid when required.

3. Damaged or Leaking Brake Line

Since brake lines are usually made of steel tubing, they can rust from:

Road salt
Moisture
Wear-and-tear

This can result in a brake fluid leak, which leads to low hydraulic fluid. This, in turn, can affect your pedal travel as it’ll require repeated pumping to generate the right amount of pressure.

4. Brake Caliper Damage

The brake caliper piston helps clamp your brake pads against the brake rotor to slow or stop the vehicle.

Braking relies on friction — which creates a great deal of heat. This heat can damage your car’s disc brake caliper over time. This brake component can also become corroded with rust if it catches moisture.

Some common signs of caliper damage include:

Your car weaving to one side when stopping
A squealing sound when braking

If the brake caliper is damaged, it could leak, affecting your brake fluid pressure.

5. Worn Master Cylinder

The master cylinder is a key element of your car’s braking system.

It holds the brake fluid, generates hydraulic pressure, and feeds it to the front and rear brakes. Essentially, it pushes brake fluid where it’s needed to help bring your car to a halt.

Over time, seals within the master cylinder can break or leak. And since the brake master cylinder is responsible for generating hydraulic pressure, having a bad master cylinder can greatly affect your brake fluid pressure.

6. Leaking Wheel Cylinder

Some cars have a disc brake system on their front wheels and drum brakes on the rear.

Drum brake systems have a drum that rotates with your wheels. The drum brake has a set of brake shoes pressed against the drum by the wheel cylinder to slow down your wheels.

Corrosion in the brake cylinder causes brake fluids to leak. The leak can reduce the hydraulic pressure, making your brake pedal feel soft.

7. ABS Modulator Issues

Vehicles with an Anti-lock Braking System (ABS) have a hydraulic assembly called an ABS modulator or ABS pump. It’s responsible for optimizing brake pressure delivered to each wheel.

Modulator damage can affect a brake valve — causing a spongy pedal.

8. Misaligned Rear Brake Shoes

Drum brakes have a self-adjuster that maintains a minimum gap between the brake shoes and drum. A worn-out brake shoe lining increases the gap between the brake shoe and drum. The adjuster then adjusts itself to maintain the required space.

If your vehicle has a rear brake drum and pumping the brake pedal improves your brake pedal feel, your rear brake shoes may be out of adjustment.

9. Faulty Brake Booster

You may also experience a spongy pedal if your brake booster fails.

Why?
When a booster fails, it can’t give you the braking assistance it is supposed to. This usually happens when the brake booster is full of fluid, hampering its abilities.

What to Do About a Spongy Brake Pedal

If you experience any of the symptoms we mentioned earlier, get your mechanic to inspect and fix spongy brake issues ASAP.

However, if you’re already on the road and suddenly experience spongy or soft brakes, rapidly pump the brake pedal with your foot.

Why?
Soft brakes arise because your vehicle’s brake master cylinder can’t generate the pressure required for efficient braking. Pumping the brake pedal should create enough pressure to safely stop the vehicle on the side of the road.

DIY Brake Repairs: Are They Possible?

While you can try to fix spongy brake issues on your own, it’s recommended that you leave the brake repair to an experienced mechanic.

Why?
Brakes are highly crucial to vehicle safety.

It’s always safer to trust in the expertise of an auto repair professional to ensure your hydraulic pressure isn’t compromised. They can diagnose leaks in your brake system and bleed your brakes with specialized equipment like a pressure bleeder.

Wrapping Up

There are several reasons why you could be experiencing a spongy brake pedal. If you notice any of the symptoms we mentioned, be sure to get a trusted mechanic to perform a brake inspection on your vehicle soon.

Fortunately, AutoNation Mobile Service is just a few clicks away!

We’re available seven days a week, and with us, you get upfront and competitive pricing. For your peace of mind, your brake repair will be covered by a 12-month | 12,000-mile warranty. Plus, you can get a brake hose replacement, rotor resurfacing, and even parking brake repairs done by a professional technician—right in your driveway!

So don’t wait.
Schedule an appointment with AutoNation Mobile Service to inspect your soft brake pedal as soon as possible.