Why is My Brake Pedal So Soft?

Why is My Brake Pedal So Soft?
Posted in: How To and Tips

A Spongy Brake Pedal

Why Is My Brake Pedal Soft and how Do I Fix It?

When you step on your brakes do they feel soft or do you have a spongy brake pedal that doesn’t take much force to push down? If so, you have likely noticed that your stopping power has significantly diminished, as well. If you are experiencing a spongy brake pedal, then you should check certain parts like the brake master cylinder, brake booster, brake lines, brake hoses, and brake caliper. Your brake pads and brake rotors usually come with a different set of issues if they are bad, like screeching noises and/or a wobbly steering wheel or rear end. Here, our DYI Mechanic discusses how to diagnose the spongy brake system to discover the cause of your soft brake pedal and how to fix it.

A Spongy Brake Pedal: Why’s it so Soft?

If you step on the brake and you notice that it’s super soft, spongy, and maybe even reaches the floor, something isn’t right. You should always get resistance from your brake. It should always be pushing back against you.

Diagnosing a Spongy Brake Pedal That Goes to the Floor

  1. Brake Fluid Level
    Let’s locate the master cylinder under the hood. It’s typically near the top of the engine and somewhat close to the driver’s side of the windshield. Now check the brake fluid reservoir and make sure the fluid is between the min and max fill lines. If you need to, you can shake the reservoir to see the fluid movement so you can see where it is. DIY Mechanic’s tip: If you are low on brake fluid, that’s usually a pretty good indicator of a leak or issues with the brake system. Leaks can be slow so it doesn’t hurt to investigate for leaks whenever performing brake maintenance. 
  2. Is the Master Cylinder Leaking?
    Check the master cylinder, brake fluid reservoir, brake hoses, and brake lines for leaking brake fluid. *
    DIY Mechanic’s Note*: Most brake fluid is a clear yellow or goldish color that will darken with age and use. Do your best to keep any dirt or debris from falling inside the master cylinder. This will help prevent gumming up the works down the road
  3. Do Your Brake Lines Have Corrosion or Leaks?
    From under the car, start at one tire and work your way the vehicle, checking each brake line for leaks and corrosion. The evidence of leaks will be obvious as there will be a wet greasy spot that will likely have dirt and debris built up around it. Corrosion can be a buildup of either white or rusty brown substance that seems to be eating through the lines. If you find brake fluid or corrosion on the brake lines, it’s best to replace them.
  4. Is Your Brake Caliper Leaking Brake Fluid? Is it in Working Order?
    Check your brake caliper for fluid leaks and make sure components are free from obstructions. The brake caliper and its parts should all be free of any brake fluid. A leak in the caliper isn’t always obvious so check any rubber boots or seals for moisture. *DIY Mechanic’s Note*: The slide bolts that the caliper halves ride on should be well-greased with a heavy grease that is similar to bearing grease so if you see that grease, that is not indicative of a leak.
  5. Do Your Brake Pads Need to be Changed?
    Check your brake pad status. Are they SUPER thin? If the pads are about used up, this could simulate being low on brake fluid. Replacing your pads could fix the issue outright. *DIY Mechanic’s Note: After replacing your brake pads, even if it fixed the spongy brake issue, check your brake fluid level. If it is a little low, go ahead and fill it up. The next time your brakes need to be replaced you shouldn’t experience the spongy brake issue due to low fluid.
  6. How Do Your Brake Rotors and/or Drum Brakes Look?
    The brake rotor itself will not likely be the cause of spongy brakes but they can give you an idea if something else in the system isn’t working properly. If the face (or flat surface) of your brake rotor is rusty or doesn’t have an almost polished appearance, that means your brake pads are not making proper contact. You will want to check both the front and back of the rotor. If one side is shiny and the other is rusty, you know the rusty side is the one not making proper contact. From there you can test the pads and caliper on the bad side and determine where the issue is. *DIY Mechanic’s Note*: If the rotor is bad, it is usually warped or pitted which will cause vibration in the steering if it’s coming from the front tires. If the back pads are warped or pitted the vibration will be less obvious but it will be from the backend, and you should notice some pulsing in the brakes. If the brake rotors are grooved, then the main symptom will be a moderate to loud grinding or screeching sound that happens mainly when you brake. Drum Brakes are a little different. You want to remove the drums and check the wheel cylinder for leaks. If you discovered a leak from the wheel cylinder it needs to be replaced. Since we already have the drum removed, check the brad pad for excessive wear and make sure the brake shoes are adjusted properly. Either of these issues will cause spongy brakes.
  7. Is There Brake Fluid in your Booster?

    If we are checking your brake booster, it’s safe to say that we didn’t find any leaks in the other areas we checked. So let’s see if your master cylinder is leaking fluid into your brake booster.

    First, you need to pop your hood and locate the master cylinder. It’s USUALLY near the windshield on the driver’s side of the vehicle. It’s a rectangular box.

    Remove the master cylinder or the hose that is connected to the booster, whichever is easier.

    There are specialty tools like borescopes that could be used but in this case, a long thin pipe cleaner, wire, zip tie, twist ties, etc. would work. Slide your selected strip inside the booster and see if it comes out clean or covered in brake fluid. If you find brake fluid in the booster, you need to replace the master cylinder, the brake booster, and the connecting hose.

  8. You May need to Bleed Your Brakes

    If air is caught in the brake system, you have to bleed them.

    There are multiple ways to bleed your brakes; gravity, pumping the brake pedals, the vacuum tool, and so on. The most successful one for me is usually the two-person method. One person pumps the brakes and the other opens and closes the bleed screws or bolts. You will likely have to repeat the procedure a few times. Just communicate with each other and you will get it done.

  9. When All Else Doesn’t Fail, It’s Probably Your Master Cylinder
    If you have found no leaks, no stuck calipers, no corrosion, no brake fluid where it shouldn’t be, and plenty of brake fluid where it should be, you probably have a bad master cylinder. If the master cylinder is bad, it needs to be replaced.

No one wants spongy brakes on the car or truck. It is scary when that brake pedal hits the floor and your car doesn’t stop. The good news is that PartsHawk has you covered on your replacement brake parts needs. From master cylinders and brake boosters to hoses, lines, brake pads, and brake rotors we have everything you need to keep your car on the road and ready to stop on a dime. After all, you have people to protect whether they are in your car crossing the street. If you have any questions or need help finding the parts you need to fix your spongy brakes, contact us.

13 days ago
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