ATV Brakes Won't Bleed - 9 Possible Causes - (2023)

The basic principle of bleeding the brakes on an ATV is quite simple. But getting your brakes to bleed correctly is sometimes easier said than done. This post covers the most common reasons your ATV brakes won't bleed and how to fix them.

Before moving on to the list of potential problems detailed in this post, make sure you have tried to bleed the brakes properly using thestandard methodsand also throughbleeding again.

You will always get the best result by combining these methods to ensure all air is removed from the system.

1. Air is trapped in the banjo bolt

Standard brake bleeding methods generally remove any air trapped in the actual brake lines. However, air can still get trapped in the fitting that connects the brake line to the master cylinder, often referred to as a "banjo bolt."

To release this air, you must hold the hand lever in the detent position, then momentarily loosen the nut that holds the banjo in place.

Tighten the nut before the lever bottoms out. I recommend using a rag to absorb the splashes of brake fluid and thus not damage the paint of your motorcycle.

2. Not enough fluid is being pumped from the master cylinder

The master cylinder on ATVs and the piston it contains are relatively small compared to what is found in a car in any other larger vehicle. Due to its small size, each pump can only deliver a relatively small amount of brake fluid.

This makes the standard brake bleeding method less efficient on smaller ATV, UTV, dirt bike, motorcycle or snowmobile brake systems.

The amount of fluid being pumped may not be enough to remove air bubbles before it bottoms out and you have to start a new pumping cycle.

3. Brake shoes not adjusted correctly

Before attempting to bleed hydraulic drum brakes, you must ensure that the brake shoes are properly adjusted. If they're not comfortable, you'll never get a good braking feel.

Set shoes to factory specifications. The adjuster on each side should be adjusted equally and the brake shoes should rub hard against the drums.

You should feel a noticeable amount of resistance as you turn the cube. If they just scrape, you may be having trouble bleeding the brakes properly because the slave cylinder can't push the shoes in far enough.

4. There is a leak somewhere in the brake system

Even the smallest leak can be enough to prevent your brakes from seizing. Check the entire system with a dry paper towel and repair any leaks you find.

5. Air is trapped in the master cylinder

To remove trapped air from the master cylinder, you must perform a bank bleed procedure.

The master cylinder bank bleeding process is a bit more thorough than normal brake bleeding, but sometimes it is necessary to remove air trapped inside.

If you've drained your brake fluid reservoir or replaced or rebuilt your master cylinder, there's a good chance that trapped air in the master cylinder is the source of your problems.

dedicate it oneseparate article on how to bleed the master brake cylinder.

6. The brake master cylinder is faulty

If you're having trouble getting fluid through the brake lines, your master cylinder is likely faulty.

Inside the cylinder is a piston with an o-ring that will wear or deteriorate over time. Requiring multiple pumps to get firm brakes further increases the likelihood of your master cylinder going bad.

Fortunately, an older master cylinder can be rebuilt, and the necessary parts are inexpensive. Most manufacturers sell kits to fit your specific device that come with step-by-step instructions.

7. Wrong handle installed

If you recently replaced your brake handle/lever, this could be the source of your problems.

Installing a replacement lever or the wrong type of lever can prevent the piston in the master cylinder from fully returning when the lever is released.

This, in turn, can prevent brake fluid from dripping down and in front of the piston. The piston will move, but it won't get fluid from the reservoir to pump the brake lines.

8. Missing copper washers on banjo bolt

If you previously opened the banjo bolt, be sure to install it correctly with a copper or aluminum washer on each side.

If installed incorrectly, it may have problems building pressure or drawing air into the brake system with each braking operation.

9. Clogged brake line or bleeder screws

Over time, your brake lines can become clogged with corrosion and dirt. If you can't squeeze a single drop of fluid out of an open bleeder valve, or if your brake fluid is flowing poorly, you may have a clogging problem.

Try disconnecting the banjo connector from the master cylinder and pumping the brake to see if the cylinder works properly. Use a rag to prevent the caustic brake fluid from ruining the paint and plastic.

If you get a steady stream of brake fluid when you squeeze the brake lever, the clog is likely somewhere in the brake line.

Before you start replacing the brake lines, it's worth removing the bleeder valve completely to see if that fixes things. Replace the clogged purge valves with new ones. Bring in the old and any car dealer will have new ones for almost free.

Additional Tips for Stubborn Braces That Won't Bleed

I'll end with a lot of last resort tips for testing if your brakes seem to be in good condition but you don't want to bleed.

Leave the brake lever on overnight

A simple trick you can try once you've tried everything else and don't want to start messing with the master cylinder is to zip or rubber band the lever in the locked position overnight.

If you're lucky, that might be enough to allow the most stubborn air bubbles to escape into the expansion tank.

With the master cylinder cover removed, slowly pump the brakes

Here's another simple trick to try before trying to bleed the master cylinder completely.

Open the cap of the brake fluid reservoir. With the reservoir full of brake fluid and all bleeder valves closed, slowly begin to pump the brakes. Watch for bubbles in the reservoir.

Keep pumping until there are no more bubbles. Reinstall the cover and test the brakes.

Gravity bleeds the brakes

Gravity Bleed is a well known method to try when all else fails. It may or may not be effective. The only way to find out is to try it.

  • First, remove the brake fluid reservoir cap and add fluid.
  • Place cups under each gauge and open the bleed valves.
  • Leave the system for about 20 minutes. Just make sure the reservoir doesn't dry out or you'll have a much tougher job of venting.
  • Add more liquid when it starts to go down.
  • Brake fluid flows slowly through the bleeder valves. Hopefully the air comes out with the liquid.
  • After filling the reservoir a few times, you can try tightening the bleeder valves, reinstalling the reservoir cap, and see if braking has improved.

The brakes still don't bleed!

If you've gotten to this point and still haven't had success bleeding the brakes, I salute your willpower!

Try overfilling the brake fluid reservoir.

I once had no luck bleeding the brakes on my KTM EXC dirt bike. I tried everything and used bottle after bottle of brake fluid. The brakes were still soft.

I then tried to fill the reservoir completely with brake fluid before proceeding to manually pump and bleed the brakes. And what do you know, after just a few pumps the brakes came back on.

I can't explain how this happened, but give it a try before you give up and take your machine to the dealer.


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