Ever pressed the brake pedal and felt that strange sponginess? Don’t worry. Spongy brakes happen all the time, and in most cases are pretty easy to diagnose and fix, assuming it’s caught early on.
We’ll go through the possible causes and a simple place to start diagnosing the issue for yourself, to save you time and money, and help save your life.
What Are Spongy Brakes?
A spongy brake, or soft or mushy brake pedal, occurs when your brake pedal feels soft or spongy as you press down on it.
A spongy brake pedal feels different from the firm, responsive feeling you’re used to when pressing on the brake pedal.
Top 6 Reasons for Spongy Brakes
Spongy brakes aren’t just annoying – they can be dangerous. If you’re feeling anything strange going on when you step on the brakes, look at the five reasons below that could be happening.
#1. Air in the Brake System.
Air is the most prevalent source of spongy brakes, but just as important as removing air from the system is determining how it got there. If you’ve recently serviced brakes, that is a strong possibility.
If not, you likely have an issue that will make a whooshing or hissing noise somewhere in the system, and you need to find it! First, bleed the brakes and see if the problem goes away. If it doesn’t, keep on reading.
#2. Damaged Brake Lines.
Several components can become damaged, but there can be no doubt, brake lines are the most common.
This is particularly true in coastal towns and for states that use a lot of rock salt. Both cause corrosion, and there is no protection on the brake lines.
The longer that goes on, the more the lines will rust, leading to leaks that allow brake fluid to escape, and allowing air to enter the system.
#3. Old Brake Fluid.
Brake fluid can last a surprisingly long time, but it won’t last forever. Some manufacturers have recommended service intervals that range from 20,000 to 30,000 miles, but it’s not that simple.
That is because, as long as the brake system is leak-free, the brake fluid can last over 100,000 miles. However, once air is introduced into the brake liquid, it begins to oxidize and adds moisture into the mix.
This is bad news for your brake system, and the more moisture is added, the more air should have entered the brake line, which is a clear indicator that you need to flush the brake system and change the fluid.
Although it may seem like there isn’t air in the brake lines, air could have caused the fluid to be contaminated beyond effectiveness.
#4. Damaged Master Cylinder.
While brake lines can corrode and leak, your master cylinder has several seals that keep everything together. A master cylinder seal can break in two ways, and then it either leaks brake fluid out of the cylinder (which can result in spongy brakes) or it leaks above the brake fluid (think of the cap) and allows air into the system.
This air not only results in issues, but it will also attract moisture, which will cause even worse brake fluid deterioration, resulting in spongy brakes. So obviously you’ll need to repair the leak and flush, and replace the brake fluid to make sure the nagging problem does not return.
#5. Damaged Brake Calipers.
Another common location for a leak to develop is around brake calipers. Brake pistons have seals (which keep the brake fluid where it is supposed to be), but if those finish degrading, you can leak brake fluid, not that this is super common, but if you did, it would be an issue.
You won’t just have to deal with spongy brakes, but you’ll also have low brake fluid levels and brake fluid spilling around the rotors and brake pads.
If you happen to encounter a leak from a brake caliper, you must fix it as soon as you can.
#6. Leaking Brake Booster.
An important part of your vehicle’s brake system is the brake booster. This device amplifies the amount of effort you put into applying the brake pedal lever.
The problem with a hydraulic-type brake booster is that if any seals start to fail, you can also have what seems to be spongy brakes, when it’s actually a drop in brake pressure as you apply the brake pedal.
Cost to Fix Spongy Brakes
Are you worried about the cost of the brakes being spongy? We’ve simplified it for you.
The cost will never be identical in every instance due to so many differences with your vehicle, where you live, and where you go for service, but these overall estimates should give you a rough idea of what to expect.
First, let’s look at the cost of a brake fluid flush and brake system bleeding! This is typically the first thing to try for spongy brakes that have air in brake lines or contaminated brake fluid. For this, you can expect to pay around $80 to $200.
In the case of more serious disc brake caliper problems, like a seized or damaged caliper, you may need to replace the caliper.
The cost of a new brake caliper is generally between $60 and $300 each, depending on where you get your car parts. Also, if replacing a caliper, you need to consider the labor to remove and install that caliper, which can also vary between $80 to $200, etc.
Perhaps you’ve found that your brake caliper damage is a result of excessive wear to your brake cylinder, and you may need to replace your brake master cylinder.
Replacing a master cylinder is probably going to cost you between $250 to $500 (parts and labor), depending on what type of car you have (make and model, etc).
In a much rarer scenario, a brake line test may show that you have damaged, rusted, or leaking brake lines. To replace your brake lines, you can expect to pay around $300 to $800 for parts and labor. Yes, that is expensive, but you should have a working braking system that is safe.
Diagnosing a spongy brake pedal
When applying the brakes, you should feel solid pressure from the start of motion all the way to the finish of motion. If you press the brakes and feel pressure changing, or it feels soft or mushy, you have a spongy brake pedal.
A spongy brake pedal feels more like a squishy brake pedal. They mean the same thing.
There’s one more test you can do to try and narrow down the source of the problem. One of the best tests to do is to turn the key off and pump the brakes a few times. Once the pedal gets hard, push down on the brakes.
If the pedal starts to sag to the floor after this, then you have a leak somewhere within the system, and you know the problem is more than just a little air that you need to bleed out of the system.
FAQs.
Q: Is It Safe to Drive with a Spongy Brake Pedal?
If you have spongy brakes, it is NOT safe to drive, and you need to repair the problem ASAP.
Spongy brakes are one of the most dangerous problems for your vehicle to have. Spongy brakes are a sign of a deeper problem, and more importantly, spongy brakes will prevent you from stopping as efficiently as you should.
Spongy brakes could mean that you have a leak, and small leaks could become big leaks with just one push of the brakes!
If your leak blows out, you will lose all brake pressure! You won’t just stop slower – you won’t be able to stop at all!
Even if your brakes don’t leak, spongy brakes mean there are air pockets forming. The soft feeling you get when pressing the pedal is simply air pockets hitting the caliper – when that happens, your brakes aren’t working.
You are going too slow, and it’s just going to get worse until you fix it.
Q: Why do I have spongy brakes after replacing calipers?
Sometimes, you may feel spongy brakes after changing your calipers. This is normal if you’ve not bled your brakes properly, or if air has been trapped while you have were working on your brakes.
If your brake lines have air in the system, then it will create a problem circulating brake fluid and provide a spongy feeling when you step on the brake pedal.
You will need to do a proper brake bleed and bleeding procedure to get the air out of your brake lines.
Q: Will my spongy brakes correct themselves?
Spongy brakes will not correct themselves and require your attention that correct the problem.