How to Diagnose a Spongy or Soft Brake Pedal

Properly functioning brake systems can be the difference between stopping in time during an emergency situation and colliding with another vehicle or object. Today’s modern vehicles utilize a variety of active safety systems, such as Automatic Emergency Braking, that rely on properly working brakes to function. Pressing the brakes on your vehicle should provide firm feedback through the pedal as your car comes to a complete and secure stop. If the brake pedal feels spongy or soft, you may have a serious issue on your hands that needs to be handled right away. 

Your local experts at are here to help you understand and diagnose a spongy brake pedal, so you can get your vehicle back on the road.

Warning Signs of Spongy Brakes

Spongy or soft brakes usually come with a variety of other warning signs:

• Brake pedal sinks to the floor during stopping

• Brakes need to be pumped to come to a stop

• Brake system warning light is on 

• Fluid is leaking from the brake lines or brake caliper

All of these conditions are often seen before or after you notice a spongy brake pedal.

What Causes Brakes to Feel Spongy or Soft?

Air being introduced into the braking system is the most common reason for a spongy or soft brake pedal. To understand why this happens, let’s do a quick lesson on how your brakes work. 

Brake components are part of a complicated hydraulic system. Pressing the brake pedal moves hydraulic fluid at a high pressure through a brake hose that’s designed to handle the pressure. On disc brake systems, this hydraulic fluid (brake fluid) then operates a set of brake calipers and brake pads that clamp down on a round rotor that spins along with the wheels of your car. On drum brakes, the pads and rotors are replaced by brake shoes that are inside a spinning drum. Over time, these pads or shoes wear out, and our Mavis technicians can replace them.

When brakes are working properly, the pedal should have a linear, smooth feel with firm pressure. Once air gets into the brake lines, the intense hydraulic pressure causes the air to compress and that feeling is translated back to the pedal as a spongy or soft feeling. Air can be introduced into the braking system in a few ways. 

Air intrusion happens naturally as you open the brake fluid reservoir under the hood to check levels or add fluid. This happens gradually and is usually fixed once the lines are ‘bled’ of air when you get your pads changed by . Damaged brake lines, most commonly from road salt corrosion, can also cause air to be introduced into the system and cause a brake fluid leak. Faulty joints, bad seals near the calipers, brake master cylinder, brake booster, or other components can also cause a brake fluid leak and air intrusion. These conditions will usually cause low brake fluid in the reservoir as well. 

Water can also cause air to be introduced into the braking system. DOT 3 brake fluid is hygroscopic, so it’s designed to attract and absorb water. This happens normally over the course of time, like air intrusion. If the brake fluid is not changed for long periods of time, water can build up to the point where the brake fluid can no longer absorb it. Since braking produces tons of friction and heat, brake fluid is designed with an extremely high boiling point. 

Excessive water reduces the boiling point of the brake fluid and causes it to boil in tough braking conditions, such as descending a mountain pass. Once this happens, the steam produced from boiling fluid gets trapped as air bubbles in the lines and can lead to that dreaded spongy brake feeling. 

Can You Drive with Spongy Brakes?

You should never drive a vehicle that has spongy brakes because the vehicle could be extremely difficult to stop or the braking system could fail completely. There are some situations where the spongy brake pedal is minor, and those situations can be handled case by case, but even a minor issue with brakes is enough for great concern. The last thing you want is your brake pedal to sink to the floor in an emergency braking situation. 

Bottom line: if your brake pedal is soft or spongy, you need to fix it as soon as possible. 

How Do You Fix a Spongy Brake?

If you suspect air has made its way into your brake lines, you’ll need to bleed the air from the lines via bleeder screws located at each brake caliper. 

This is a complicated process that requires advanced mechanical knowledge, specific repair procedures, and specialized tools for the job. Since most modern vehicles have an advanced anti-lock braking system, this further complicated brake bleeding.  If you’re an intrepid DIYer or a shadetree mechanic, this process may be in your wheelhouse, but the majority of folks will want to take their vehicle to a professional at to get this job done properly. 

Other fixes include swapping old fluid with new fluid, which again, is relatively simple, but could be a challenge for someone who’s never done the job before. Old brake fluid gets contaminated with water and must be swapped out regularly. Broken brake lines can cause fluid loss and air intrusion, which can be repaired by Mavis or done on your own if you have the skills and tools to get it done. Repairing or replacing leaking components, such as the calipers, master cylinder, and wheel cylinders may also be common fixes for a spongy brake pedal. 

How Often Should You Get Your Brakes Checked?

A good rule of thumb is to have your brakes checked every 30,000 miles by the professionals at . We will give your vehicle a thorough inspection during an oil change or other service and let you know if there are issues with the brakes. If you do your own maintenance, be sure to check the brake fluid regularly, and swap it out every 30,000 miles or on the manufacturer’s suggested schedule. 

Mavis Offers the Best in Brake Maintenance Services

At Mavis, a team of experienced professionals can be found at convenient locations in your neighborhood for all things brakes and tires, including brake inspections, brake pad changes, brake fluid changes, brake repairs, and much more. If you suspect an issue with your brakes or brake pressure, schedule an appointment.