Brake bleeding problem

Just converted to CR style brake routing. While I had the old line off my wife helped out by pumping the brake lever to, "get all of the stinky old oil out"....Besides making a mess, air was sucked into the master cylinder. I bought a vacuum pump bleeding tool and sucked about a qt of fluid through the bleed screw, but the lever still feels spongy on test ride. Is there a way to "bench bleed" the master cylinder? Any help would be great....getting a new wife has already been considered.

Did you try removing the reservoir cover and tapping on the caliper, lines and the reservoir. I know mine was feeling super spongy and when I did that a bunch of bubbles came out of the line and the brake feel was back.

If Hootna's trick doesnt work, and Id try that first becaue it'll be less messy than mine try this.

Get a squeeze bottle and reverse bleed the unit from the caliper up. Basically you squeeze fliud into the bleeder in the caliper up through the whole system backwards. Your going to overflow the resi. but, youll get your bubble too.

haven't tried that (tapping), will try, if it works, does anyone want to buy a 50$ hand vacuum pump...It's not Dr. Joel Caplan's, but it might work.

I had the same problem and trust me I tried every trick that has been mentioned in this forum. I finally asked a friend that is motorcycle mechanic and he did it in about 30 minutes. He looked at my pump that I purchased and laughed. He knew how frustrated I was because he said he once had the same problem. The steps below will show you how to do it. Since then I have done a few of my friends bikes and they are amazed at the results.

Step 1: Take off the caliper and pull the brake cable as straight as you can.

Step 2: Use the bleeder screw with you basic technique until some fluid comes through. Once you have fluid there is no need for the bleeder screw again.

Step 3: Pry open the brake pads with the top of the master cylinder off. Have somebody watch to see if any air bubbles come out.

Step: 4: Place a small wrench in between the brake pads and have somebody pump it up until it is tight.

Step 5: Repeat steps 3 and 4 until you stop getting air bubbles.

You should see drastic results in 30 minutes. Make sure you are using new fluid.

I definately agree with the "reverse" bleeding. It will cut your time in half, theres actually a good article in MotoCross action on how to do it.

You also don't waste as much brake fluid either.

The reverse bleed is a very good point. Air bubbles get trapped in the line and won't go down, nor do they float up.

And tapping is important as well since the bubbles like to stick to the things.

Lastly, push your pads (pucks) all the way in. This will push out all the old fluid and air that never gets cleansed under normal bleeding.

A good bleed (on an opened system) may take you upwards of 30 minutes, so be patient.


Thanks for the tips. I ended up using the vacuum pump by sucking from the master cylinder side while siphoning fluid thrugh the bleed screw, tappin like mad the whole time and completely pushing the brake pads out/piston in.......great results, the braided brake line has great fade resistance.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now