HOW TO BLEED BRAKES AFTER NEW BRAKE LINES
— What you need to know —
By Rick Sosobee and the staff of Dirt Wheels
When it comes to performing maintenance on your ATV or SXS, one particular selection of parts will need close attention. That would be the brake system. Your brakes are very important, and they could be your salvation when your talent runs low while showing the trail just how inexperienced you are. Performing regular maintenance like changing brake pads or a brake disc is simple and typically does not require brakes to be bled. However, when you start to open the hydraulic lines of your braking system, you will find a much different project altogether. Allowing any air at all, even a bubble as small as a sweet pea, to enter the brake line could lead to a disaster when you need stopping power.
Bleeding brakes can be frustrating and time-consuming if you do not have the proper skill set or experience, not to mention a few special tools to help speed along the process. Recently, we replaced the brake lines on one of our off-road machines. Once installed, we found ourselves having to completely fill the lines with fluid and properly bleed the system.
It is vital that you do not allow the brake fluid reservoir to run low while you are bleeding the air out of the system. If you do, you will have to start over. You will have introduced the air into the system yourself. We removed the lower, driver’s-side shock bolt to lift the shock and make reaching the fluid reservoir easier.
Always start with a fresh new bottle of brake fluid. Since we were refreshing the entire system, we got a large bottle. We couldn’t get to the reservoir easily, so we used a smaller bottle to fill and maintain the level in the brake fluid reservoir.
A brake bleed screw can typically be opened with a 5/16th or sometimes 8mm wrench, but use caution, as these little devils are easy to damage if over-tightened.
The cheapest aid you will find to collect the brake fluid excess is a small bottle like this. They are typically under $10 at any auto parts store. A small magnet holds it to any steel near the caliper.
To use the bottle, you will need a second person to employ the traditional brake bleeding process of pump (pumping the brake pedal until it is firm and holding) and dump (loosening the brake bleed screw to evacuate the fluid and air) to get all of the air out. Allow the pedal to hit the floor. Hold it until your partner closes the bleed valve. Repeat process as needed. However, it may take longer doing the process with just the bottle.
The bottle works well if you are just bleeding the brakes, but if you must refill the system, a vacuum pump like this Mityvac is a much more efficient way to go. We paid $75 for ours at a parts store, but they can be found for under $40, and Amazon has several non-branded ones for just under $20. These kits typically have a cup or reservoir of their own to collect fluid as it begins to come out of the bleed screw to save you from making a mess on the shop floor. This type of tool will make getting the air out of the line very simple and fast.
You connect the tubing from the vacuum pump to the brake bleed screw via the tubing provided in the kit. You open the bleed valve and pull the fluid from the reservoir down to the brake caliper with a few pumps. The trick is to be sure you keep the fluid level in the reservoir high enough. Don’t run low or out and pull air in with the fluid. Being patient and taking your time with the process will ensure you get it done quickly and back out on the trail. The nice thing is, the clear tubing allows you to see any air in the fluid immediately.
Begin at the rear wheel farthest from the master-cylinder fluid reservoir. For our Polaris, it is the passenger’s side rear. Then do the other rear wheel, the passenger’s side front and finally the driver’s side front.
Once the fluid is coming out of the brake bleed screw with no air bubbles, simply tighten the brake bleed screw and recheck the fluid. Bubbles this size will cripple the system. Even though this process is very close to being completed, you still want to check for a firm brake pedal. If it feels spongy, you may need to use the bottle and the pump-and-dump method on each wheel. Once the pedal is firm, you can finish up.
After you have a firm pedal feel, make sure the bleed valves are closed. Then simply fill the brake fluid reservoir to the proper level with fluid. As for bleeding the brakes, some choose to elevate the machine according to the reservoir location, as air will eventually rise to the top and out into the reservoir. Be sure to add the bleed-screw caps back onto the screw when you are finished (if you have them) to keep dirt from filling the tiny hole there. Now it is time to ride, but be sure to test the braking on your off-road rig before getting too far from the shop.