Motorcycle Is Leaking Brake Fluid (Causes & Fixes)

If you notice your motorcycle is leaking fluid, you might feel overwhelmed with concern. That’s certainly understandable, as nobody wants their bike to break down. Luckily, finding out what’s causing your bike to leak brake fluid isn’t as complicated as it might sound.

In a nutshell, you’ll have to start by finding the leak. In most cases, you’ll need to clean the area in order to find the leaking component. Once you’ve found the leak, it’s just a matter of finding the right part your bike needs and replacing it. This can be done yourself or by a certified professional, like a mechanic.  

There’s nothing more stressful than having motor vehicle issues. It’s even more troublesome if you depend on your bike as your sole method of transportation. Even so, you can take a deep breath.

Our guide will walk you through the process step by step. We’ll explain everything from the possible culprits of the leak to the actual process of fixing it. Rest assured, you’re not the only one whose bike is leaking brake fluid — it’s a common problem that’s completely fixable.

Reasons Why Your Motorcycle Is Leaking Brake Fluid

If you notice your motorcycle is leaking brake fluid, try not to panic. One of the first steps you should take if you find yourself in this position is to consider why this leak happened in the first place. There are many potential causes for a motorcycle to leak brake fluid, so it’s critical to pinpoint what exactly is going on.

Motorcycles leaking brake fluid

Keep in mind that your bike has a closed brake system. That means the fluid should never leave or leak out. Instead, the brake fluid is used every time you ride and should only ever be changed out for new brake fluid. It doesn’t really matter if you see brake fluid leaking out or if you realize that the motorcycle’s brake fluid levels have dropped. Either way, this isn’t a good sign.

That’s because brake fluid levels really shouldn’t have low readings. Low brake fluid readings will typically only show up if there’s a leak. However, it could also be a result of very worn-out motorcycle brake pads.

The best way to determine the cause of the leak may be to go ahead and have your brake pads inspected. If nothing is wrong with the brake pads, that pretty much confirms you have a motorcycle brake fluid leak on your hands.

Once you confirm that your bike is leaking brake fluid, you’ll want to do a little more investigating. Unfortunately, there are many culprits when it comes to brake fluid leaks.

1.   Damaged Brake Master Cylinder Reservoir

Your bike’s master cylinder is a location worth inspecting for leaking brake fluid. However, it’s not easy to find. Because the bike’s brake fluid can leak down the actual motorcycle, it’s possible that the brake components — such as the brake lines — could be completely covered.

Brake master cylinder reservoir

2.   Failed Piston Seal

A motorcycle’s piston is an extremely important part of your bike. The bike’s brake elements — namely the disc brake caliper, the drum brake wheel cylinder, and the master cylinder — are reliant on the piston to function.

Your bike’s piston has seals that essentially control the brake fluid, as the piston is activated by that fluid. However, those seals can cause a brake fluid leak just from regular wear and tear damage over the years.

3.   Worn Out Brake Pads, Shoes, Rotors, and Drums

As mentioned earlier, your motorcycle’s brake pads can be worn down to the point where they’ll leak brake fluid. But they’re not the only thing that can become damaged over time. Other common offenders include the bike’s drums, rotors, and its brake shoes. These can all cause your bike to leak brake fluid.

4.   Damaged Brake Lines or Brake Hose

Damaged brake lines or a damaged brake hose can also be a reason for leaking brake fluid. If you’re not familiar, the brake fluid is carried to the piston through those brake lines. So, since these brake lines aren’t protected from the elements, it’s possible that they’ll wear down and start to leak brake fluid.

To find the source of the leak, try checking to see if there’s liquid dripping down the brake hose. If the hose is indeed leaking, it’s a good idea to buy a new hose as soon as you can.

5.   Damaged or Loose Bleeder Valve

In your motorcycle’s front calipers, there are some small caps called bleed caps that are used to “bleed” out liquid within the bike’s system. However, these round caps can become detached, loose, or otherwise damaged. As you might’ve guessed, this can cause fluid to leak. To confirm this, you can look around for an oily liquid or buildup.

6.   Faulty ABS Pump

Your motorcycle has something called ABS pumps, which have parts in the bike’s brakes. These parts are extremely important, as they hold and carry the brake fluid. If you have an ABS pump that’s faulty in any way, the seals of the ABS brake reservoir can succumb to regular wear and tear damage over the years, which can cause your motorcycle to leak brake fluid.

How Can You Fix Brake Fluid Leaks?

If you do have a brake fluid leak, you’ll want to fix it immediately.

The good news is the process of repairing your motorcycle’s brake fluid leak is typically a routine procedure. The hardest part is finding the brake fluid leak, so if you’ve already done that, you’ve won half the battle.

Before you change out any parts, you need to actually find the source of the leak. Once you do confirm it, however, you’ll want to replace any faulty parts as soon as possible. If you buy the wrong parts, you’ll just be wasting not only your money but your time as well. That’s precisely why it’s so critical to locate the culprit of the leak.

To make it easier to find the leak, plan to clean everything. This will save you so much time in the long run, as it’s easier to find the brake fluid leak if everything is clean. With brake fluid leaks, it’s tough to find the source if there’s fluid everywhere. After all, there could be more than one leak, but you’d never know unless everything is cleaned.

After this step, you can go ahead and check your bike for the source of the leak. If you’re having trouble, try building pressure within the system by pulling the brakes. This can help reveal the brake fluid leak’s location.

Once you find the leak, replace the parts involved. However, keep in mind that you’ll let air into the system if you open the brake system. To mitigate this, after the system is closed, bleed it out.

Safety Tips for Handling Brake Fluid

In general, brake fluid isn’t very safe. That’s why it’s so crucial to understand the risks involved.

Before you even begin, it’s absolutely imperative to use both goggles and gloves — along with other protection — in order to handle the brake fluid safely.

For one, it’s toxic to your skin and other things, and it’s also very corrosive. That means it’ll eat away at paint and plastic, among other surfaces and materials. Always clean up your bike’s brake fluid if it gets on anything that it shouldn’t. And yes, that includes both your skin and eyes.

Although it’s not likely, getting brake fluid in your eyes or on your skin can be dangerous, and at the least, it’ll cause redness and pain. That should be a good motivator for you to wear appropriate protection.

It’s probably equally unlikely, but brake fluid is very poisonous. If by chance you do swallow your bike’s brake fluid by accident, you should call a local poison control center near you. These centers are available every day for 24 hours. Call right away if this happens.

Poison Control can be reached at (800) 222-1222. Don’t risk your health by not calling immediately. At the end of the day, your bike’s brake fluid could actually kill you if ingested. That’s because the corrosive liquid will severely damage your organs, particularly your kidneys and liver. You’ll definitely need immediate medical attention if you swallow brake fluid.

It goes without saying that you should never keep brake fluid where pets and children can access it.

Should You Bleed Your Bike’s Brake Fluid?

If your motorcycle’s brakes are leaking brake fluid and you replace a part of your bike’s brake system, you’re inadvertently allowing air into the system, which is very dangerous.

Here’s why. If you have a mix of both air and brake fluid, the cylinder won’t work correctly due to the air bubbles. If there’s lots of air in your bike’s system, the motorcycle won’t work properly, and the cylinder probably won’t be able to move.

So, should you bleed your bike’s brake fluid after fixing a leak? The answer is a resounding “absolutely.” It’s critical that you bleed your bike’s brakes once the leak is fixed. Luckily, it’s not a very complicated process as long as you’re familiar with the steps.

If you look near the bottom of the motorcycle’s calipers, you’ll be able to see the bleeder valve. Once you locate it, connect part of the hose from the bleeder valve into a reservoir, such as a bucket or even a bottle. Next, put some pressure on your bike’s brakes before opening the bleeder valve. However, make sure you only open it about half a turn instead of opening it all the way.

Once you do this, you should notice both air and a bit of your motorcycle’s brake fluid escape. After that, you’ll want to release the brake’s lever and shut the bleed valve. Repeat the process as many times as necessary to ensure that the only thing coming out of the bleeder valve is your bike’s brake fluid.

When you’re doing this, make sure you’re watching the fluid reservoir. Air will get sucked into the system all over again if you let the fluid levels get too low. Once that happens, you’ll have to start the whole process again.

You’ll know when the system is totally drained when you don’t see any more air bubbles. 

In order to be totally prepared to solve your brake fluid leak issue, you’ll need to be aware of the costs involved.

The Average Cost to Fix a Brake Fluid Leak

The average cost to fix your motorcycle’s brake fluid leak will depend on a few factors. First and foremost, the make and model of your car can affect the price. Usually, the costs will be around a couple of hundred dollars.

But it also depends on which motorcycle part is the culprit. When considering the cost of fixing a brake fluid leak, be sure to remember that you’re paying for the replacement part as well as the labor costs.

Including both labor costs and the price of the actual bike part, you can expect to pay around $525 to $700 for a brake caliper leak. If you’re fixing a master cylinder leak, prepare to spend about $400 to $550. For both a brake line leak and a rear drum cylinder leak, you can expect to pay an average of $150 to $200.

How to Get Your Brake Fluid Leak Fixed

Although you can definitely fix your bike’s brake fluid leak yourself, it’s usually best to see a professional. That way, you don’t have to worry about diagnosing the leak, finding the correct parts, handling the brake fluid, and bleeding your bike’s brake fluid.

Fixing a brake fluid leak can be a drag for many people, and having a professional evaluate your motorcycle cuts out any potential confusion.

An expert like a mechanic can tackle a brake fluid leak by locating it and repairing it for you. Before you choose a mechanic, you should make sure they offer service warranties for their services. You’ll also want to ensure that the replacement parts and brake hardware they’re using are high quality and up to standards. It’ll help if you can find a mechanic that’s ASE-certified. If you’re unfamiliar with ASE, that stands for Automotive Service Excellence — a certification that auto experts earn when they finish their training and other requirements. 

They’ll take all the guesswork out of fixing a brake leak so you don’t have to worry.


When your motorcycle is leaking brake fluid, it’s hard not to feel concerned or worried. Still, fixing a leak isn’t as complicated as it seems as long as you do your due diligence to understand the process.

Either way, fixing a brake fluid leak is a necessary step to take to get your bike to that point. That’s going to include cleaning the area, diagnosing the leak, and replacing the faulty parts. Even if you’re uncomfortable fixing the leak yourself, there are many professionals you can trust to take care of your bike

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