bleeding brakes

c did this last year when I rebuilt my master cylinder with a kit I got from Chacal (which works great i might add) But i replaced the sight glass yesterday and sealed it up with a brake-fluid-resistant sealant and now I've refilled the master cylinder with fresh brake fluid and I'm trying to bleed the brakes. Both holes (large hole, and pinhole) in the master cylinder are clear.

Here's my methodology:

1) fill up and cover master cylinder
2) open bleeder valve
3) squeeze brake lever. while holding down brake lever, tighten bleeder valve
4) release blake lever.
5) repeat steps 2-4 until brake fluid starts shooting out of the bleeder valves.

what's going wrong:
whenever i do step (3), i can hear air coming out of the valve. Whenever I do step (4), i can hear the air being sucked back in. Brake fluid is not leaving my reservoir and going into the brake lines. This is driving me nuts. What am I doing wrong???

 

When I rebuilt my master control I was having the same issue. My son noticed that the banjo bolt was not tight and air was getting in the line. Once tight it went a lot better (still took some time to get the fluid moving). If you disconnected the line you might look in that direction.

You could get a pump from Harbor Frieght for bleading breaks, I haven't tried it but others swear by it.

 

did you do a bench bleed on the master cylinder before going on the bike? I hear that not doing this can cause some issues?

 

please define bench bleed.

 

From what I've read you basically run a hose from the outlet on the MC into the fluid reservoir and pump the MC until all of the air is out of it. It's like priming it before attaching it to the rest of the brake system. I have yet to do it on mine, but will be this weekend.

 

to simulate what I'd be doing with the bleed valves, i disconnected the brake line from the MC and plugged the hole of the outlet with my thumb. Squeezed the lever, moved thumb off to release pressure, put thumb back on, squeezed the lever...repeat.

I did this several times and got a lot of pressure build-up with the initial pumping, but mostly, it just ended up just sucking back on my thumb instead of pulling fluid from the reservoir. I double checked and triple checked that the pin-hole is free.

I'll see if i can find a piece of hose that I can do that with.

in the meantime, any more suggestions or enlightening thoughts are appreciated!

 

Also, check the line connection at the MC, there needs to be two washers, one on either side of the brake line. I was missing the inner washer, which caused my system to do the exact same thing. It was sucking air into the top of the line right at the MC, which wouldn't let me bleed the system correctly or build any pressure to engage the caliper piston. Added the missing washer and it all went away.