As an ATV owner, it’s a good idea to learn a few basic mechanical skills, such as being able to bleed the brakes when needed.
This job is relatively easy to do and can save you quite a few bucks on mechanical expenses. Follow this guide and you have a great chance at succeeding with just about every brake bleeding job.
What does bleeding the brakes mean after all?
Hydraulic brake systems use special brake fluid to transfer the energy from your hand or foot, and down to the brake caliper. The fluid is essential for proper brake function.
Inside the caliper, there is a piston that’s being activated by the brake fluid when pressure is being applied. The piston will then press the brake pad against the brake disc, creating friction to stop the bike.
Bleeding the brakes means letting some of the brake fluid out, either to remove air or to replace it with new.
When do you need to bleed the brakes?
There are two main causes for having to bleed the brakes on your ATV:
To remove air from the brake lines
Brake fluid cannot be compressed, but air can. If even the smallest bubble of air enters the system, the brakes will not function as they should, but rather feel soft and squishy. To get all of the air out of the system, we need to “bleed” the brakes.
Air may enter the system if you replace or disassemble one or more components connected with the brake line, such as removing the brake caliper for a service. Or you may have a brake line simply come loose, allowing air to enter the system.
Please note that air should not get into the system under normal operation of the ATV. Therefore you have to locate and address the cause of the leak before bleeding the brakes.
To replace old or bad brake fluid
Another common situation where knowing how to bleed the brakes comes in handy is when it is time to replace the old brake fluid with new. So-called flushing the brakes.
Brake fluid is hygroscopic, which means it absorbs water over time. In addition, it breaks down when being exposed to heat. The fluid closest to the brake calipers is the most affected because of the heat produced when breaking.
Healthy brake fluid should look clear or with just a slight amber color. If it looks like cola, it is well overdue for being replaced.
Bad brake fluid will negatively affect the performance of your brakes, so make sure you replace it in time. Luckily this job is both cheap and usually quite easy to do.
It’s a good idea to completely replace the brake fluid on your bike every time you change your brake pads or at intervals according to your ATVs service manual.
Bleeding front brakes vs bleeding rear brakes
Most ATV’s will have one master cylinder for the front brakes up on the handlebar, and another one for the rear brakes. The reservoir for the foot pedal is often located a bit away from the actual cylinder unit.
The setup will vary from model to model. Some bar- mounted master cylinders will operate both the front and rear brakes as well.
The method for bleeding them, however, is pretty much identical.
To identify how your bike is set up, simply follow the brake lines from the brake caliper to see where they end up. You need to address each reservoir connected with the brake you are having problems with.
If you are not sure where your problem is, you might as well bleed the brakes on all four wheels. Then start with the caliper the furthest from the master cylinder and move against it.
The manual or standard method
Let us begin with the standard method for bleeding any type of hydraulic brake system. It requires almost no tools or previous mechanical experience. Just follow the steps below:
Tools and parts required
- A jack to get the ATV off the ground.
- A wheel nut tool, preferably a hand tool as the air or electric torque wrenches tend to be a bit powerful to be used on ATVs.
- The correct hex or Phillips bit, or a small impact driver.
- 8mm wrench for the bleeder (most ATV bleeders are in 8mm). Both a boxed end wrench and a flat nut wrench will work.
- A clamp or a friend to press the brake lever
- Brake fluid according to manufacturer requirements. Refer to your service manual where this will be listed. It should also be marked on the brake reservoir cap. It’s always best to stick with the same type as when the bike was new. If you don’t have the manual: Most ATV uses regular DOT4 brake fluid.
Optional (but recommended):
- A piece of 5/16 inch clear vinyl tubing inserted into a small container such as an empty oil-bottle. Use it to collect old brake fluid for proper disposal. Not only will the environment thank you, but you will keep your shop and ATV clean as well.
- Latex gloves. Brake fluid is quite rough on your hands.
How to bleed ATV brakes:
1. Jack up the ATV.
Start by jacking up the ATV and remove the wheels where you are bleeding the brakes. It is possible to bleed the brakes without removing the wheels, but you will get much better access to the bleed nipple with the wheel out of the way. If this is your first time bleeding the brakes, I always recommend removing the wheels.
2. Remove the brake fluid reservoir cap.
You will need to add new brake fluid as the old goes out. The lid on the reservoir up on the handlebar is held in place with two hex screws. Be careful as the threads strip quite easily.
Depending on the age of the bike and the time since the screws were removed, they may be grown in there pretty good. This is where the small impact drivers come in handy. Find the correct bit and use the driver by giving a light tap.
This will knock loose any corrosion and open the screw slightly at the same time. One knock is usually sufficient. The reservoir for the foot pedal usually has a twist cap that simply unscrews by hand.
3. Clean the cap and rubber diaphragm thoroughly.
You do not want to contaminate the system with debris, dirt or water when reassembling later on.
4. Top of the brake fluid up to the maximum level mark.
Pay close attention so that the brake fluid level in the brake fluid reservoir never drops below minimum during the process of bleeding the brakes. You may need to top off the reservoir several times before you are finished.
It’s recommended that you reinstall the lid before moving to step 5. While it is possible to pump the brakes with the cover off, you run a great risk of quirting brake fluid all over your bike if you pump the brakes too hard or too fast.
5. Pump the brake lever or foot pedal 3-4 times, depending on which you are bleeding.
Remember to pump carefully if you do this with the lid open! Then keep the lever activated by hand or by putting on a spring-loaded clamp to keep it under tension.
6. Open the bleeder valve.
Start with the valve that is the furthest from the brake fluid reservoir. It is located on top of each brake caliper and is opened by turning it anti-clockwise about half of a turn. You should see brake fluid squirt out of the bleeder.
7. Close the bleeder valve when the brake lever or foot pedal reaches about 80% of its overall travel length.
Do NOT overtighten the bleeder. The threads in the aluminum brake calipers strip easily!
8. Repeat until the brake fluid that comes out of the bleeder is completely free of air bubbles.
This may take a while, depending on how much air there is in the brake lines.
9. Follow the same procedure on all four wheels.
Some bikes have just one combined brake caliper for the rear wheels.
10. Top off the brake fluid reservoir up to the maximum mark.
The mark may be a line found inside the reservoir, or an inspection gauge on the side. Other reservoirs have a gauge on top of the reservoir cover, that is white when brake fluid levels are low, but turns black when the correct level is reached.
11. Replace the lid and rubber diaphragm.
Make sure it is seated properly. Do not over-tighten the bolts. You are now done and can reinstall the wheels.
Downsides with manually bleeding the brakes
The manual method works fine most times, but not always. It comes with a few annoying downsides as-well:
Not enough fluid being pumped
The master cylinder and the piston inside it on an ATV is quite small in compared to the one you find on a car on any other larger vehicles. Because of its small size, it is only able to pump a relatively small amount of brake fluid with each pump.
This makes the standard method of bleeding brakes work less efficiently on smaller brake-systems found on ATVs, UTVs, dirt bikes, motorcycles or snowmobiles.
The amount of fluid being pumped may not be enough to move the bubbles of air out before you bottom out and have to start a new pumping cycle.
It takes forever
It will take about 10-15 minutes to completely flush the brake system on an ATV using the standard method. It will take even longer if you do it on your own.
If you’re having problems removing all of the air, you may be looking at several hours of struggle before you eventually succeed or give up.
It’s working against gravity
When you pump the brakes, you force the air downwards against the bleeding valve. Air is lighter than brake fluid and will always want to go upstream, away from the bleed valve.
Combined with a small pump, you may not be able to get all of the air down to the bleed valve.
So then what? Luckily there is another cheap and easy method for bleeding the brakes that work very well.
Vacuum bleed ATV brakes
Vacuum bleeding is another cheap and easy way you can use to bleed the brakes properly.
In addition to the five first bullet points listed for the standard method, you will also need a hydraulic brake bleeder tool.
These come in a variety of shapes, but they all work by the same principle: they suck the brake fluid down and out through the bleed valve using a vacuum.
Some models use a hand pump to create the vacuum. They will also have a one-way check valve that allows brake fluid to flow out of the brake caliper without letting air back into the system when you release the pump.
Other models connect to an air compressor to create the suction effect.
This is how you do it:
- Step 1-4 is identical to the standard method.
- Put the 8mm wrench to the bleeding valve so that it is ready.
Hook up the vacuum pump to the bleeder valve. Make sure the pump is connected to an air compressor if required.
- Activate the pump and open the bleed valve about half a turn. You should see bubbles of air squirting out and into the container of your tool.
- Keep an eye on the reservoir level. The vacuum pump will empty the small reservoir in just a few seconds.
- If levels are starting to drop low, re-tighten the bleed valve, de-activate your tool and add more brake fluid to the reservoir before you continue. Read this post if you accidentally let your reservoir run dry.
- Continue bleeding until a steady stream of clear brake fluid flow inside the see-through hose connected to the bleed valve.
- Tighten the bleed valve before you remove the vacuum tool.
- Repeat on all brake lines you wish to bleed.
- Top off the brake fluid reservoir to the maximum mark and reinstall the lid and rubber diaphragm.
Now you should be ready to tackle almost any brake bleeding jobs. But from time to time, even the vacuum pump won’t be sufficient to bleed all of the air out of the system.
Before taking the bike to your dealer it’s worth reading through this post on what to do when you’re not having success bleeding the brakes using the methods described above.
Alternatively, you can try to reverse bleeding the brakes on your ATV.