Why do brakes become soft and spongy?

That the brake pedal feels soft, rubbery, or spongy when you press it is a clear symptom that something is wrong with the brake system. This is not only annoying, it can be dangerous and affect your ability to stop the car in time.

In this article, we'll go over the most common causes of soft brakes, what it means, and what you can do about it.

The most common reasons why brakes feel soft

1. Air in the brake system

The most common reason for a soft brake pedal is air that has entered the brake system. The brake system is based on hydraulic pressure, meaning that fluid is forced through lines. But air is compressible, which means it “squeezes” when you step on the pedal — and that makes the pedal feel soft instead of firm.

Air can enter the system if:

• Brake fluid changed or serviced without proper bleeding
• There are small leaks in the lines or connections

Solution: the brakes must vented so that all air is removed and the brake fluid once again forms an unbroken hydraulic system.

2. Something is sticking in the brake system

Another common reason is that something is stuck in the brake system, for example:

• A piston in the brake caliper stuck
• A sliding bolt that does not move properly
  This means that the brakes do not work evenly or completely correctly, and you may notice that the pedal feels soft or spongy when you brake.

When a piston seizes, it can pull fluid in the wrong direction or not return properly, affecting the hydraulics in the system.

3. Low brake fluid level or leak

If the brake fluid is too low (for example, if the fluid is leaking from a brake line, piston, cylinder or clutch) the system does not receive the correct pressure. This results in a soft pedal and reduced braking performance.

Signs of leakage are:

• Fluid under the car at the wheels or under the hood
• The brake fluid level in the reservoir drops

4. Worn or faulty parts

Other reasons why the pedal feels soft could be:

• Worn brake pads or brake discs
• Master cylinder fault where the sealing rings have stopped working
• Flexible brake hoses which expands under pressure

These factors can all affect how effectively the brake fluid can transfer force from the pedal to the wheels.

Why is it important to fix soft brakes?

A soft or spongy brake pedal means that the brake system is not working at full powerIt can:

• Extend the stopping distance
• Making braking less controlled
• In the worst case, this can lead to dangerous situations in traffic.

So it is not something to ignore, but have a workshop look at the car as soon as possible.

Quick checklist if your brake pedal feels soft

Try the following (or ask the mechanic if they can do it):

✔️ Check the brake fluid level
✔️ Look for signs of leakage
✔️ Request bleeding of the brake system
✔️ Check brake calipers and pistons
✔️ Check brake hoses and brake parts

Summary:

Cause	Short explanation
Air in the system	Air in the hydraulics makes the pedal "soft"
Tough components	Pistons or slide pins do not move properly
Leakage / low fluid	Lost pressure causes spongy brake pedal
Worn parts	Wear on pads, hoses or cylinder affects feel

Niemi Bil offers tire service, new tires, tire changes and tire hotels in several locations. If you want to be sure that your car is in good condition, you can read more and book service at our workshops.

Things in this article that we can help you with:

Niemi Bil has workshops in most locations where we sell cars. We carry out all types of work on most car brands and can also offer services such as tire changes, tire hotels, service, repairs, and installation of additional equipment.