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What causes brakes to feel spongy?

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Updated 25 Mar 2021

Rowan Johnstone

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Spongy brakes. It’s the dreaded feeling of pressing your foot down on the brake pedal and expecting firm, consistent resistance whilst your car comfortably comes to a stop. Instead, the pedal just sinks down towards the floor of the car and your brakes just don’t perform as well as they normally do.

This can be dangerous and there are a few things that might be causing that spongy brake feeling. It’s best to get yourself to a mechanic or get a mobile mechanic out to you as soon as possible.

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Air in the brake lines

This is the most common cause of spongy brakes. When air gets into the brake lines it can prevent the brake fluid from flowing freely and consistently. This inconsistency in brake fluid is what causes the spongy or soft brake pedal feel.

If this is the cause, a mechanic will need to bleed the fluid from the brake lines and replace it. When the old fluid is removed, so is the air that’s causing the spongy brakes. Replacing the brake fluid has other benefits as well. Fresh fluid helps preserve other parts of your braking system such as the ABS and master cylinder.

Leaking brake calipers

Calipers, being made of metal, can rust over time and compromise their structural integrity. If this happens, the internal piston seal can leak fluid, causing the spongy feeling in your brakes. New brake caliper/s will need to be fitted and a qualified mechanic will make sure the necessary steps are taken to ensure proper braking performance is restored.

Leaking brake lines

The most common cause of spongy feeling brakes is air in the brake lines so, naturally, if the brake line is broken or leaking, this will also have the same effect. Brake lines are made from metal, so they can rust and corrode over time, similar to brake calipers. When this happens, small holes can appear and let fluid escape, which in turn leads to a loss of hydraulic brake pressure. This loss of brake pressure will cause your brake pedal to feel soft and spongy.

Leaking wheel cylinder

If you’ve got drum brakes on your car, you’ll have wheel cylinders as well. Corrosion inside these wheel cylinders can result in brake fluid leaking and, similarly to leaking brake calipers, can cause a loss in hydraulic pressure.

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ABS hydraulic malfunction

Your car may have an anti-lock braking system (ABS) fitted. If anything within the hydraulic assembly of this system, which contains many valves and solenoids, fails, it could cause the system to not operate properly and lead to spongy-feeling brakes.

Rear brake shoes

We’re back to drum brakes again here. If the rear brake shoes aren’t self-adjusting as they wear, they may be out of alignment. This may cause your brakes to feel spongy, or make the brake pedal travel further than normal. The brake shoes need to be routinely checked, and a professional can make sure they’re adjusted correctly. Something you can do, however, is to make sure you’re using the handbrake regularly. Engaging the handbrake works to adjust the brake shoes automatically.

All in all, if you’re experiencing spongy brakes or a brake pedal that’s going all the way to the floor, you need to get a qualified mechanic to take a look. Brakes are one thing that you definitely want working properly, as it could be the difference between a nasty accident and you getting home safely.

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Written By

Rowan Johnstone

On weekdays Rowan can be found in the AutoGuru office, driving content and growth with the rest of the marketing team.

On weekends you’ll probably find him in the garage with his dad restoring a 1958 Ford Star Model Customline or enjoying a cruise through the Gold Coast hinterland on his Suzuki GSX-R600.

Despite his passion for being behind the wheel (or handlebars), he looks forward to the day when he can commute to work in his own driverless car.