GO***N Rear MC!!!

[johnboi71]

Long time no posting, I have been checking in from time to time though.
My bike has been sitting for a while now and I decided to get it back on the road, starting with the brakes.
I have been trying to get my rear MC bled out for days now and am totally frustrated. I even went out and bought a mity-vac to help. I rebuilt the MC and the caliper and made sure all was clean, new K&L kit in the MC. With my bench setup, I can stick the hose attached to the caliper into a jar of fluid and it draws fine. I connect to the MC (Not sure if I was fully bled on it) and nothing! I am pulling a solid 22inches of vacuum and it is not drawing fluid

I did have it drawing from the MC one time, and when I pushed on the pump/ piston, I lost the draw. I pulled the hose from the MC and tried to bench bleed it, but it doesn't seem to be working.
I filled the MC and poured fluid into the hole where the banjo goes. I try and pump up the pressure and nothing is really happening. Am I pumping to fast? How much stroke does the piston need to build pressure? I thought I had it at one point as I had pad pressure on my blocking board, but when I put it back on the bike-nothing

I have read several threads, but nothing popped out about how much stroke and if it is possible to blow the prime by pushing the piston in too far.
The front was a pain, but nothing like this.

HELP ME PLEASE BEFORE I LOSE MY MIND

[mjpxs11sh]

been there, done that! without Mity-Vac. this is what worked 4 me. disco caliper banjo, pump pedal and suck on banjo till u get fluid. doesnt taste good, but i was desperate and so r u. i filled caliper reservoir, reinstalled banjo and filled MC and pumped the air out by bleeding. u could use ur M V to bleed. i heard it works great. if no fluid when sucking banjo, then u know theres an issue with MC rebuild. u just have to step away and chill and go back into it. good luck

[Stepka]

Have you taken off the hose from the master and see if anything comes out? if it does than remove the line from the caliper and see if anything comes out. If it flows out of the master but not the hose its a bad hose.

[SFerinTEXAS]

Long time no posting, I have been checking in from time to time though.
:

My advice is don't take any advice from anyone that's been here less than 2 years.. Of course most over 2 years have shut up overwhelmed by the tribbles.

http://en.wikipedia.org/wiki/The_Trouble_With_Tribbles

[Stepka]

My advice is don't take any advice from anyone that's been here less than 2 years.
http://en.wikipedia.org/wiki/The_Trouble_With_Tribbles

MEH!!!! I'm just trying to help.. I have worked on cars for 12 years and sometimes people forget some diagnostic procedures.... Hell with the bike sitting the line may have collapsed internally, hell its just rubber

[Stepka]

I miss read the post... sorry, thought you were trying to bleed thought the caliper with the master still in.

[WMarshy]

If you have the MC on the bars and the line hooked up to it, I would disconnect the banjo at the caliper and see if the MC will push any fluid through the line. It should drain the MC from gravity alone if there is no obstruction. Sometimes its easier to let gravity do the work... if you get some flow after pumping the MC hook it back up to the caliper (have the caliper installed on the disk) with the banjo. Before you hook it back up, dump some fluid into the banjo bolt hole to top off the caliper. Everything will work a lot easier if you try to get as much air out of it as possible. With the bleader closed on the caliper, pump the MC several times with the cover off of it. Dont mash the handle to the bar, only go like 75% and release, you should see some bubbles come up through the MC. Then hook up your Might Vac and try to draw some through the system. Be very careful not to drain the MC too much and suck air into the line, the MC doesnt hold very much. Another tip is to put some plumbing PTF tape on the bleader threads to get a good seal with the caliper. Be advised, the break fluid will eat it up over time, so I like to remove it when Im satisfied with the blead... Hope thats enough to get you started, no guarantee my method is "the best" or only way to get the breaks to blead, just somet ideas to think about. GL

[johnboi71]

Thanks Marshy, but I am working on the REAR not the front. Kind of hard to mount it to the handlebars. I am also bench bleeding the system off the bike. Thanks anyway dude.

[SFerinTEXAS]

Hydraulics can have no air .air will rise up in fluid, You have to help let that happen. Just think like a bubble that wants to escape.

[johnboi71]

I guess specifically what I am asking is.......... Can I push the piston in with my finger, during bench bleeding, that the MC would lose it's prime??

[XS1100 Newbie]

If you push the piston in to far, you could have the rubber on the piston flip over, The book cautions against pushing to far on the front, so i would assume that it would be the same on the rear. I would try to gauge a 3/4 stroke. You may have to disassemble and check the piston.

[WMarshy]

Thanks Marshy, but I am working on the REAR not the front. Kind of hard to mount it to the handlebars. I am also bench bleeding the system off the bike. Thanks anyway dude.

Sorry, must of missed that you were working on the rear. I would put it back on the bike personally, and still follow the tips I gave you about filling the caliper as much as possible and checking flow from the MC through the hose and not over compressing the pedal (only 75%)... I completely disassembled my rear MC last year and had no problem putting it back together and getting it to work... did you make sure all the internals were put back the way they came off?

[johnboi71]

Thanks all, I have taken the MC apart a couple of times to make sure the seals were right. I have gone more than 3/4 sroke on the depth though when trying to bleed by hand.
The weird part to me is I can get vacuum to suck fluid through the caliper and line, but it won't suck out when I connect the line back to the MC.
I guess I will take it apart again and try yo bench bleed the MC one more time. I have never had this much problem bleeding a brake system

[New2Me]

I just rebuilt my rear brakes (lines and all) and was having issues getting the mc to build pressure. I didn't prime the system like I should have but did use a mighty vac. After a couple days of alternating bleeding with the MV and pedal it finally built pressure. I also had to twist some small wire around the vac tubing at the bleeder because zip ties weren't cutting it.

I imagine if the seals were installed upside-down you would not get any pressure. If the lines are clear then maybe the banjo bolt is the problem.