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Why Do I Have a Soft Brake Pedal? Causes and Solutions

If you own a car and drive it regularly, you must have experienced a soft brake pedal at some point. This can be frustrating and dangerous, especially if you are in the middle of driving and need to stop quickly. It could be something minor or need brake pads replacement. But there could be bigger issues going on with your car when the brake pedal is soft.

Learning the possible causes and available solutions for spongy brakes will give you confidence and guidance when the problem occurs the next time.

What Are the Causes of Soft Brake Pedal?

There are many different things that could be causing a spongy brake pedal. Here is a list of the most common reasons for this issue and what you can do about them.

Cause 1: Issues with the brake lines.

Damaged brake lines can cause the pedal to feel soft when you are pressing on them. This means that your car is constantly trying to pump fluid through a damaged line. As there is not enough fluid, the hydraulic pressure falls, causing a loose brake pedal. A leak in your brake system will happen if rust has formed holes or corrosion has eaten away at the metal of the pipe.

Have all rusted pipes replaced immediately because they could fail soon. In fact, if you see any rusty spots start forming around these parts, take care of this problem right away. Taking early steps may save you from the expenses of changing all pipes.

causes of soft brake pedal
There could be holes in the brake lines. (Credit: mweekend)

Cause 2: Rust in the disc brake calipers.

The disc brake caliper is the part that squeezes the brake pads against your car’s discs in order to stop it. If you notice a soft or spongy feeling when braking, this could mean corroded disc brake calipers.

Leaking fluid from damaged piston seals on the inside of your rear brake calipers can make them feel soft while braking. In case of a leak, there will be wet spots near the outside edge where oil has dripped onto the pavement.

If it’s just a worn-out seal, changing it will fix the problem. However, if the rust sets in and damages the calipers, don’t wait too long before going out for replacements.

Cause 3: Worn out master cylinder.

A worn master cylinder can cause a soft brake pedal. A car’s brake system is hydraulic-operated, meaning that the braking power in your foot has to make its way through cables and hoses before it ever reaches the brakes.

The master cylinder pressurizes the brake fluid to generate hydraulic pressure to the front and rear brakes. So, when you push on the pedals, they stop appropriately. If a vehicle’s master cylinder starts wearing down, it may not be able to adequately deliver enough pressure for hard braking — which will ultimately result in a soft pedal feel or a complete lack of resistance from the brakes (brake failure).

When the issue is with the master cylinder, there will be an internal brake fluid leak from a piston seal or an external leak. In this situation, get your vehicle for a service appointment with an experienced technician. It has to be properly diagnosed by an expert.

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Cause 4: Rusty and leaking wheel cylinders.

What causes spongy brakes? Be alert for a leaking wheel cylinder too. If your car has drum brakes on the rear wheels, there should be wheel cylinder pistons and brake shoes inside the drum. The pistons cause the shoes to press against the drum; thereby, helping the brake pedal to function.

Wheel cylinders can develop holes and cracks because of corrosion. Hydraulic pressure cannot build up when brake fluid leaks through a hole, causing a brake pedal that feels soft.

Cause 5: Worn out rear brake shoes.

In the case of drum brakes, the rear brake shoes need to touch the metal “brake drum” for the brake pedal to make the wheel slow down. When the brake shoes wear down or get broken, the distance between them becomes too wide. They no longer touch the drum surface, which will make for a softer feel in braking.

If it’s an adjustment issue, you can fix this by applying the parking brake from time to time. When the parking brake engages, it automatically adjusts the brake shoes. If the shoes are damaged, contact a mechanic.

Cause 6: Malfunctioning ABS hydraulic assembly.

An ABS system has an ABS modulator, consisting of several solenoids and valves. One or multiple valves may stop working because of a corroded component or the failure of an internal part. Sludge in the brake fluid can also stop a valve’s functionality, resulting in a loose pedal.

brake pedal is soft
The ABS module in a VW car. (Credit: Bavarian Performance Specialists)

It’s simple to fix. Take your car into a competent garage for an inspection of all ABS components including lines, valves, and pumps. They’ll be able to identify any problems quickly.

Cause 7: Bleeding the brakes

Sometimes, you will get a soft brake pedal after bleeding the brakes. During the bleeding process, air can be trapped inside the hydraulic brake fluid system, especially in the brake line, which is the reason for the pedal to feel spongy when pressed. Replacing the brake lines or hoses can also import air inside the system.

To solve this problem, you have to flush the brake fluid from the system or bleed by using the vacuum method. Clean and fresh brake fluid protects various components in the braking system and ensures a long-time operation of all parts without any trouble.

Conclusion

A brake pedal can be soft for a variety of problems and there are solutions to each one. Be alert for the symptoms to catch them at the early stage. If you’re experiencing a soft brake pedal, bring your car in for an inspection, so the technician can determine which fixing method works the best. Take prompt action as soon as you can detect the problem. Timely service from experts will help you avoid costly repairs down the road.

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