Does your brake pedal sink to the floor? We know – it is an unsettling feeling. While any problems related to the brakes are serious, considering the potential consequences of a sinking brake pedal, I would say this is an extra cause for concern. So before continuing driving with brakes that you can’t be sure of, diving in and solving the issue is imperative.
In this article, you’ll learn the four most common causes of why the brake pedal goes to the floor, what you need to do about it, and other helpful advice.
So without further ado, let’s get started.
What Are Possible Reasons A Brake Pedal Goes To Floor?
The most common reason a brake pedal goes to the floor is due to an external or internal leak in the brake system. An external leak can occur in any part of the system, including the master cylinder, brake calipers, or even the brake lines themselves. An internal leak means likely means the master cylinder is at fault.
While these are the most common reasons, it’s not the only possibility. So we made a complete list for you here that also covers a few tips on solutions.
1. External Leak In the Brake System
If you have a brake pedal that goes to the floor, an external leak is probably the first thing to check for, and it means there should be brake fluid leaking out somewhere. The brake fluid transfers the force from your foot to the brake caliper.
A leak will inevitably cause the braking system to struggle to acquire the required pressure and the brake pedal to sink to the floor.
What you want to do is to get under your vehicle and check all four wheels to see if there’s any leakage from the brake caliper or rubber lines. If your vehicle has leaking drum brakes, they would be wet at the bottom.
If everything seems dry, you then want to check for rusty brake lines that potentially leak. But unless you live in an area with a lot of road salt in the winter, they generally don’t rust.
The next thing would be to check for internal leaking.
2. Internal Leaking Master Cylinder
If your brake pedal goes to the floor but has no leaks, the culprit may be a leaking brake master cylinder. The master cylinder provides hydraulic pressure, which travels through your brake lines and activates your brakes.
If there is an internal leak in the master cylinder, the brake fluid will leak backward around the rubber seal protecting the piston instead of pushing on the calipers.
The master cylinder will therefore struggle to achieve the necessary hydraulic pressure. However, there’s often a simple way to tell.
If the fluid level in the master cylinder reservoir is full, you have put an X in the checkbox for external leakage, but your foot is still slowly going to the floor with normal pressure on the brake pedal. It’s safe to say that you have an internal leak in your master cylinder.
A brake master cylinder can start leaking internally due to a number of reasons, including wear and tear, age, or loose or missing cap. But most times, it’s because of worn seals. So if this is the case, you need to replace it.
Mechanics Tip: Buy a brand new quality master cylinder and not a rebuilt one. Rebuilt ones don’t tend to last as long and sometimes don’t even work at all. The same goes for unreliable, cheap knockoffs.
3. Air in the brake lines
While the external or internal leak is the most common cause and air in the braking system usually causes an abnormal feeling in the pedal, it can sometimes be the reason a brake pedal goes to the floor.
When air makes its way into your brake system, it causes air pockets that take up space and negatively disrupt the pressure resulting in reduced effectiveness of the brakes, which makes them feel soft and unresponsive.
However, the brake system is designed to be airtight. So when air does get into the brake lines, it’s usually during repairs or because of worn or damaged brake components, such as worn brake pads or a faulty master cylinder.
However, I’ve been working on cars where it turns out to be the wheel cylinder (which is a component of a hydraulic drum brake system) sucking in air. But it didn’t leak.
To fix the issue, you need to replace any faulty parts. After that, all the air must be bled out until only brake fluid remains in each brake system component. This involves pumping up the pressure and opening the bleeder valve to release any trapped air.
You also want to ensure the brake fluid is in good condition and not contaminated, as this, too, can cause brake issues. If you want to learn more about contaminated brake fluid, you can read more about it here.
4. Misaligned Brake Shoes
Does your car have rear drum brakes that were recently worked on or serviced? If so, and if you now find that the brake pedal goes to the floor, it could be because your brake shoes are misaligned. Jiffy Lube agrees with me on that.
So if you suspect that this is the case, you should have the brakes inspected. Contact the person or repair shop that performed the brake service and tell them about your situation.
However, if there’s due to worn or damaged components, you’ll first need to repair or replace them to restore proper alignment.
When Should I take My Car in for Repair?
If you find yourself in a situation where the brake pedal goes all the way to the floor, it’s always recommended to take your car in for repair as soon as possible.
Stopping your car relies on your brakes, which in turn relies on the brake fluid transferring the pressure from your foot to the calipers, which squeeze the brakes together.
So to ensure the safety of yourself, your passengers, and other road users, it’s important to check the issue out immediately. In other terms, this is one of those things you DON’T want to put off until it’s too late!
Now, this doesn’t mean you can’t do it yourself. But it’s important to remember that this should not be attempted by someone unfamiliar with brakes, as incorrect work can worsen things. If you’re uncomfortable attempting this yourself, it’s best to take it to a professional for assistance.
Can I Drive When Brake Pedal Goes to Floor?
Under no circumstances should you drive a vehicle with a brake pedal that has difficulty achieving pressure or sinks to the floor. This indicates a serious brake problem and should immediately be addressed and repaired. Neglecting to do so could lead to serious safety risks and be highly dangerous.
How Much Will this Cost to Get It Fixed?
Generally speaking, it can cost anywhere between $100 and $600 to fix a brake pedal that goes to the floor, depending on the extent of the damage and the type of car. However, it is recommended that you have a qualified mechanic evaluate the problem to get an accurate estimate.
With that said, it’s hard to say what cause would be the most expensive to fix. If there’s brake fluid leaking from the caliper, rubber lines, or rusty brake lines, you’re probably looking at about $200 to £300.
If you need to replace the brake master cylinder, you don’t want to go with the cheapest one. So expect to spend about $100 to $150 for labor and about $150 to $250 for the part itself.
If you simply have to align the brake shoes, you might only have to pay for the work of doing so, which would come down to about $100 to $150. But if the brakes have taken damage, the cost could quickly add up to a few hundred dollars.
Keep in mind that these are only cost estimates, and the cost can vary depending on many factors, such as location, the quality of the parts, who performs the job, etc.
Other Possible Situations Where Brake Pedal Goes to Floor
Over the years, I have worked on hundreds of cars with various brake problems. From time to time, I received calls or messages from people wondering why the brake pedal goes to the floor after changing brake pads, installing a new master cylinder, etc. So I thought it was worth mentioning here.
After Changing the Brake Pads
Suppose your brake pedal goes to the floor after changing the brake pads, and there are no leaks. In that case, chances are the master cylinder was damaged when you pushed the caliper piston back and forced the brake fluid in the wrong direction. This means the MC needs to be replaced.
After Installing a New Master Cylinder
After installing a new master cylinder, you want to make sure to properly bleed your brakes to get rid of any air in the system. However, if the brake pedal goes to the floor after doing so. In that case, the new master cylinder may be defective, and chances are you bought an old repaired master cylinder or a cheap knockoff.
After Bleeding the Brakes
Let’s say you properly bled the brakes and made sure to properly screw back the bleed nipple, but the brake pedal sinks to the floor. It indicates an internal leaking master cylinder. But before replacing it, check for any visible signs of wetness or leakage around the brake calipers and brake lines.
When the Engine Is Running
If the brake pedal is hard but goes to the floor as soon as you turn the engine on, you can think it has something to do with the brake booster or its check valve. But as I mentioned earlier, it could also be the wheel cylinder or something else sucking in air. This will likely result in a lot of air when bleeding the brakes and will probably keep coming every time you bleed until the issue is resolved.
Can ABS Cause Brake Pedal to Go to the Floor?
Yes, ABS can cause the brake pedal to go to the floor. On some make and models, the ABS uses a series of solenoids and valves to isolate the brake pedal from the rest of the brake system in situations when the ABS engages. So if you have a problem with your isolation valves, the brake pedal might sink to the floor.
Can a Brake Booster Cause Brake Pedal to Go to Floor?
A brake booster doesn’t usually cause a brake pedal to go to the floor. The brake booster’s job is to increase the force from your foot to the master cylinder with vacuum pressure, making it easier for you to brake. So if it stops working properly, you’ll most likely find it harder to press on the brakes.
Can Brake Pedal Go to Floor with No Leaks?
A brake pedal can go to the floor with no leaks if there is an internally leaking brake master cylinder. This means the brake fluid bypasses back into the reservoir when pressing the brake pedal, often caused by worn seals. Replacing the master cylinder should fix this issue.
Finding your brakes with no hydraulic pressure is a nightmare. But when this happens, knowing the most common causes will often let you figure out the cause pretty easily. While you might need a professional to help you repair it, it’s at least no repair that typically breaks the bank. And considering the consequences, the cost shouldn’t be anything more than a necessary expense.
Thanks for reading. Please tell us about your experience in the comment.