Motorcycle Brakes Won't Bleed [Reasons Explained]
Bleeding brakes is meant to get rid of the air in the hydraulic brake system. Ideally, you should replace the old brake fluid with new fresh brake fluid too.
While working on my motorcycle, I've encountered a few common issues that can cause brakes to not bleed properly. This can cause major problems because it will force the wheels to turn while the brakes still contact the rotors.
Air bubbles can also get trapped in the brake fluid. This reduces the hydraulic pressure and makes the brakes less efficient. If you’re dealing with this issue, we can help. Here are some of the common reasons why motorcycle brakes won't bleed.
Air Trapped in the Brake System
I've found that air trapped in the brake lines is one of the main reasons my brakes wouldn't bleed. Air in the brake lines compresses, causing soft or squishy feeling brakes and sometimes preventing effective braking altogether.
I always ensure I remove any air bubbles from the system when bleeding the brakes. Typically, this air gets trapped in the brake line causing it to flow into the brake fluid and toward the rear brake.
How Do You Identify This Issue?
To identify this issue, pull the brake lever and carefully analyze how it feels. If you notice a softer or cushioned movement, we have air in our brake lines.
When this happens, we have to take a new approach. The traditional method of using a bleed nipple for bleeding brakes won’t work.
Clogged Brake Lines or Hoses
Another issue I've encountered is clogged brake lines or hoses. Debris or corrosion can accumulate, leading to blocked lines and preventing the brakes from bleeding.
This usually happens because of water leaking inside the brake line. To fix this, I usually inspect and clean the brake lines and hoses to ensure a smooth flow of brake fluid.
How Do You Identify This Issue?
The easiest way to identify this issue is by manually inspecting the brake lines. Look for damages, tears, rust, and corrosion. The motorcycle brake lines need to be in good condition for the brake system to work how we want it to.
Malfunctioning Master Cylinder
When I first experienced brake bleeding issues, I found that a malfunctioning master cylinder was to blame. The master cylinder generates the pressure needed in the braking system.
If it's not working properly, it could prevent the brakes from bleeding effectively. There is no way to effectively bleed brakes unless the master cylinder works as it should.
How Do You Identify This Issue?
Determining if the master cylinder is bad is tricky. Typically, the check engine light will come on to let the rider know. If not, leaks or brake fluid contamination is common.
I always check the braking performance. Because we lack proper brake pressure, it should be noticeable that something is wrong with the bike.
Damaged Brake Caliper Seals
Lastly, damaged brake caliper seals can also cause brake bleeding issues. These seals are crucial to maintaining airtightness in the braking system; without them, the needed pressure can't be achieved.
When the seal breaks, it will cause a leak. Simply replacing the old fluid with new brake fluid won’t solve the issue. We need to repair the seals first to maintain proper brake pressure.
How Do You Identify This Issue?
I recommend inspecting and replacing the damaged seals to restore the brake system's functionality. The brake calipers can wear out or get damaged easily because they are left exposed.
Common Brake Bleeding Mistakes
Novice riders with very little brake bleeding experience make these common mistakes. Try to avoid these to keep your brake system in better condition.
Incorrect Brake Bleeding Order
In my experience, following the appropriate brake bleeding order is crucial for success. Typically, you should start with the caliper furthest from the master cylinder and work your way toward it.
The bleeding order is less important on a motorcycle because they only have two sets of brakes. But you should pull the front brake lever first and move to the rear brake next.
Following this order ensures that air bubbles are effectively removed from the system. It can take longer to get the air out of the brake system. This could overflow the master cylinder with brake fluid too.
Not Applying Enough Pressure
I've learned that sufficient pressure needs to be applied to the brake lever during the bleeding process. This pressure forces the brake fluid to move through the system, pushing out any trapped air bubbles.
If the pressure applied isn't adequate, air can remain in the lines, causing the brakes not to bleed correctly.
Failure to Close Bleeder Valves Properly
One mistake I've made in the past is not closing the bleeder valves properly while bleeding my motorcycle brakes. It's essential to close these valves before releasing the brake lever to prevent air from re-entering the system.
Improperly closed valves contribute to an unsuccessful brake bleeding process. In fact, leaving the valves open while bleeding is the most common rookie mistake.
Old or Contaminated Brake Fluid
Finally, I've discovered that using old or contaminated brake fluid can negatively impact the brake bleeding process. The brake fluid absorbs moisture over time, which can lead to a decrease in performance and difficulty in bleeding the brakes.
How To Properly Bleed Motorcycle Brakes
Knowing how to bleed the brakes properly is crucial for a smooth and safe ride. So, let me share the steps I followed:
Find Specs & Details In The Owner’s Manual
Before we start, you should always open the owner’s manual to find the exact specs for your bike. This includes torque specs, procedure recommendations, and other necessary brake fluid information.
Prepare The Master Cylinder
I always get started by checking the brake fluid reservoir to ensure it is full. Filling it with fresh fluid is vital since low levels or contaminated fluid can cause braking issues.
You can do this by removing the master cylinder top. This is a good way to check if the bike has enough brake fluid too.
Attach Bleed Pipe To The Bike
Next, we need to attach the bleed pipe to the bleed valve on the bike. You can do this by locating the brake caliper bleed valves.
These small fittings have a rubber cap and are found on the calipers. I removed the cap and attached a clear hose to the valve, leading the other end into an empty container.
Use The Brake Lever For Pressure
Next, I gently pumped the brakes a few times to build pressure. While holding pressure on the brake lever, I used the wrench to open the bleed valve slightly, releasing fluid and air bubbles.
I immediately closed the valve and released the lever, repeating this process until no more air bubbles were visible in the hose. You can open the bleed valve to allow the fluid to flow freely too.
Close Valve & Repeat Steps
Make sure to close the valve when the fluid stops. This should relieve pressure and bleed the brake system correctly.
A motorcycle has two sets of brakes so when you finish, move on to the next and repeat the same process. Always make sure to keep the brake fluid reservoir full.
Finally, after completing the process on both wheels, I topped off the brake fluid reservoir, tightened the cap, and cleaned any spilled fluid using a clean rag or cloth.
How to Fix Motorcycle Brake Bleeding Problems
Here are some tips to consider to fix the brake bleeding problems you’re dealing with much faster.
Inspecting Components
When I first notice that my motorcycle brakes won't bleed, I always start by inspecting the brake components for any visible issues. I pay close attention to the brake lines for any signs of leakage, which might be a cause of the problem.
Another thing I look for is contamination in the brake fluid. Dirt or debris can prevent proper bleeding. This is a common issue for older brakes.
Applying Proper Bleeding Techniques
Using the right techniques can make all the difference when bleeding my motorcycle brakes. I have found the manual, vacuum, and powered vacuum methods all helpful in different situations.
Motorcycle owners must keep the brake fluid reservoir filled and ensure no air in the lines, as this can cause bleeding problems.
Replacing Necessary Parts
If my inspection reveals a problem or my efforts to bleed the brakes have been unsuccessful, I consider replacing the necessary parts. I have had to replace the brake lines or copper washers to fix a leak.
Another critical thing to keep in mind is brake pad replacement. I always monitor my brake pads and replace them when they get low, as worn-out pads can cause issues with braking and bleeding.
