How to: Bleeding The Brakes

Bleeding your brakes is quite easy and very important. Air in the lines can cause brake fade and failure, which can result in severe injury. However, bleeding the braking system is not to be used as a "quick fix" for other problems. Proper understanding of the master cylinder and brake caliper units is paramount. Brake bleeding is normally reserved for AFTER the braking system has been overhauled and/or rebuilt. These systems work in conjunction with each other and should be serviced, properly, together. Do Not overlook one for the other. Though separate, these units should be treated as one.
NOTE: Read manufacturer's suggested DOT fluid rating and NEVER mix two different types of brake fluids. If you plan to bleed your brakes, bleed them entirely and replace fluid from a new, unopened container. Only use brake fluid!! Not oil, not hydraulic fluid, ect., only brake fluid.
Brake fluid is a dangerous substance. DO NOT let it come into contact with painted surfaces. Immediately clean up any spill and wash hands thoroughly. Keeping a "more than normal" clean area when working with brake parts is very important!
Makes sure you read this in it's entirety and thoroughly before beginning.

This will cover the standard procedure for bleeding brakes. Both vacuum bleeding and "oil can" bleeding is covered at the end of this tutorial. Ok, lets begin.

First, read what type of DOT rated fluid you will need. It is on the master cylinder (m/c) reservoir cover or in your motorcycle owners manual (mom).


Next, you will want to reset the brake m/c position. When you open the m/c fluid will spill everywhere if the m/c is not level.


Place the bike on it's center stand and/or level the machine as much as possible. Using a 10mm socket, loosen the bolts enough to move the m/c level, slighty retighten to hold it in place.


Now, remove the 4 bolts that hold the m/c cover on. Note: I have replaced my original bolts with new, stainless steel M5 / 3mm, tappered allen head. The originals will strip!


Check the fluid level of the m/c and clean it out if necessary.


Find a sutible container to hold brake fluid in.


The object of bleeding the brakes is to remove air from the lines, thus you want to push fluid thru, and out of, the system. To do this you must attach one end of a tube, preferably clear, to the bleeding nipple...


...and submerge the other end in a container full of brake fluid.


This will allow air to exit the caliper and be forced under the fluid level. Since the end of the tube is submerged, air can not go back into the system once the tube is full of fluid. Try to keep the end of the tube submerged under the fluid level. If the tube comes out it is ok, just make sure that the fluid does not flow back into the system, bringing air with it. This can be avoided by tightening the nipple during the bleeding process.

4 step process here. 1) You will be pulling the brake lever in. 2) opening the bleeding nipple and pumping the lever. 3) retightening the nipple (just snug). 4) Releasing the lever.

So, using a 5/16 wrench, pull the lever in...

...and open the nipple. Do not completely remove the nipple. Just "crack" it open enough to allow fluid to flow out. Pump the lever a few times. The tube will fill with fluid and go into the container. Again, try to keep the tube submerged and do not let the fluid fall back into the caliper letting air in. Make sure you have fluid in the tube at all times. This will insure fluid does not flow back in followed by air. NOTE: Because the tube is on the nipple you will need to use the open end of the wrench. Opening the nipple with the wrench, with the tube on, is a pain, but after a few times it becomes easier to work around.

Then tighten the nipple while holding the lever in and then releasing the lever. Since the nipple is on top of the caliper, and the tube needs to curve down, tightening the nipple each time prevents fluid from falling back into the caliper and letting air in. It also keeps you from having to constantly pump the lever in order to prevent air going back in. Believe me, you will understand once you do this.
You will need to do this several times.
You want to do a little "dance". So it's "lever, nipple, pump-pump, nipple, lever", repeat.
Pulling the lever in pressurises the system, opening the nipple lets air and fluid escape, closing the nipple keeps fluid and air from going back in (Kind of a secondary safety), then release the lever. You may want to pump the lever a couple times to push air down to the nipple.
NOTE!!!! make sure you are watching the m/c reservoir. DO NOT let it run empty. You will need to keep adding fluid throughout this process. If you let it run dry, air will go into the system and you will have to start over.

What am I looking for?
You want to get all the air out. To know when this has happened you will, 1, see no more air bubbles coming out of the nipple and through the tube. And 2, the brake lever will no longer feel "spongy". If you have to "pump" the lever to build-up pressure, air is still present in the system. Everytime you pull the lever in it should feel nice, smooth, and be the same "pull" pressure each time. Remember to tighten the nipple each time. Do not "wrench" it tight, just snug it. This makes it a little easier to manage. Especially if you have to stand up and refill the reservoir.


Once all the air is out, no more bubbles and no spongy feeling, top off the reservoir with fluid.



Then put the cover back on and tighten the bolts.


Collaborative article written by members of XS650.com / 2011

 

After you have completed these steps you can remove the tube. NOTE: Make sure the nipple is tightened before removing the tube.


Be sure everything is tightened correctly!!
Make sure you properly clean up all the brake fluid, especially on painted parts. It will eat right through it!!! If you get fluid onto the rotor remove it with brake cleaner. Brake fluid can contaminate the brake pads.


Be sure to readjust the lever and m/c at the handle bars, tightening the 2 bolts securely.


And you're done. Good job!!


These are important tips, so please read!!

Only use new brake fluid with the correct DOT rating.
Spongy brakes usually means all the air is not out of the system, however, old brake lines will also cause a spongy feel. Replacing them with new lines is a good idea. You want consistency each time you pull.
If you have to "pump" the lever to get it to a nice feel, air is still present in the system. It should pull and return the same everytime.
Be careful when you take the machine out the first time. Go slow and check, check, check!!!
If you see fluid coming from anywhere, look for a leak and retighten if necessary.
Check the brakes the following day. If the brakes are noticeably more spongy, or need to be pumped to build pressure, you might have a leak caused by a bad line or a faulty master cylinder.

Alternative ways to bleed the brakes:
There are also several alternative ways to bleed the brakes.

Lever Type Oil Can:
An oil can bleeder is an easy way to remove the air. Since air rises to the top you can force the air from the caliper to the m/c. This is called "back bleeding". So, if you have replenished the system with new fluid, this is a good way of final bleeding. Or, upon checking the fluid, and it is low, this is a good way to fill the m/c reservoir and bleed the system at the same time.

Lever type oil cans can be bought just about anywhere. Be sure to use a new, unused can. These are made for oiling parts, so be sure there is no oil in the one you are using. The oil can damage the brake system.

Note: This needs to be done with a very low level of fluid in the reservoir. You will be forcing fluid from the caliper into the reservoir.
Fill the oil can with new, fresh brake fluid. Using a piece of clear tubing, the same as used in conventional bleeding, attach one end to the oil can and secure it with a small hose clamp. The other end will be attached to the bleeder nipple and also secured with a hose clamp.

Attach the end of the tube, using the clamp, to the nipple. Slowly open the nipple a 1/2 and very slowly pump the lever on the can. Squeeze slowly. If you forcefully pump the can you will overflow the reservoir and "fountain" brake fluid.
This will force the air to the top and out of the m/c reservoir. This will also be adding fluid to the system, thus filling the m/c reservoir. If all the air (bubbles) have not been removed, and the reservoir is full, you can use a small turkey baster to carefully remove some fluid and then continue.

Once all the air bubbles are out, and the reservoir is filled, tighten the nipple, then remove the clamp and hose. Replace the reservoir top, ensure everything is properly tightened, and clean up spilled fluid. Note: Be sure to label the oil can, and baster if used, with a "For Brakes Only" label, or something similar, to ensure it is not accidentally used for other projects or placed in the kitchen.

Using the MityVac Vacuum Bleeder:
You will need the MityVac vacuum Bleeder pump, short hose, catch reservoir, long hose.

1. Put your 8mm wrench on the bleeder, but leave the bleeder closed.
2. Place the long hose on the bleeder.

3. Fill the brake reservoir
4. Pump the handle about 20 times to build vacuum.
5. Use the 8mm wrench to open the bleeder.
6. Air bubbles and fluid start to flow out. When the flow begins to slow, close the bleeder.
7. Repeat this process, steps 3-7.
8. After you close the bleeder, after bleeding the second time, you should have good pressure at the lever.

Note: Due to the air gap around the threads of the bleeder, you'll likely see bubbles even when all the air is out of the system. This can be lessened by putting grease around the bleeder or teflon tape, but I don't find it necessary to get a proper bleed. Just be aware of this.
This is a very simple way of bleeding the brakes.
Warning!! You should not use vacuum pumps with "Speed Bleeding" nipples.

You can also do a "Finishing Bleed" this way:
1. Remove the cover on the master cylinder.
2. Remove the caliper.
3. Hold the caliper with the piston facing down.
4. Gently Squeeze the piston into the caliper bore.
5. Operate the brake lever to push the piston back out. Not too far, of course.
6. Repeat 4 and 5 until your arms fall off.

As you do this procedure, you will see air bubbles in the master cylinder reservoir even if you did the more traditional bleeding method for hours. The caliper piston will not blow out when you operate the brake lever. In fact, you can operate it several times for each cycle of the procedure.

You can also do this procedure from time to time without having to open the bleed screw if you suspect some air got into the system, which can happen in a rough ride if you apply the brakes and the tiny hole in the master cylinder reservoir gets unported.

A caliper rebuild how to.
Collaborative article written by members of XS650.com / 2011

 

LOL, guess it's 'cuz I grew up on a dairy farm......moo!!!