Master Cylinder failure. Please help

[jasondo]

Just two weeks from a 1000 mile road trip, I just ruined my master cylinder by creating too much back pressure pushing back the pistons that it no longer builds pressure. I mean nothing like it was empty of fluid . how do I fix this? It makes a strange noise now also

[jasondo]

Is it possible I just got a whole lot of air in the line? Should I leave the cap off and allow it to flow downhill over night? I was pumping the lever without the cap and let run dry for a few pumps before I noticed.

[jasondo]

OK crisis averted. Just a whole lot of air sucked in the line.

[riceburner]

Is it possible I just got a whole lot of air in the line? Should I leave the cap off and allow it to flow downhill over night? I was pumping the lever without the cap and let run dry for a few pumps before I noticed.

we've all done it....

[CycleRob]

jasondo, It would help if we knew ABS or not and what bike/year you have, for any questions in the future.
About air in the system, here below is a copy-n-pasted relevant paragraph from
a retired motorcycle mechanic's fully detailed brake service post: http://r1150r.org/board/viewtopic.php?f=26&t=30659

"Most owners freak out about disconnecting the brake lines and loosing reservoir fluid, getting air in the system and then not having enough brake fluid or time to bleed their way back to a "solid pedal" (normality). That's because you are not doing it right. You DO NOT need a vacuum tool like a MityVac, even if the master cylinder reservoir and it's piston bore is totally empty and/or you are installing new brake lines. Think. Think like an air bubble. It is very hard to push air bubbles DOWN and out the bleeder. It is VERY easy to push air up-n-out the master cylinder reservoir fluid. Use the caliper(s) with pistons 3/4 fully extended by clean DOT4 fluid BEFORE taking the components above them apart. If the master cylinder is fluid filled have the lever/pedal partially depressed to stop banjo boss outflow anytime before the lines are disconnected. Then you just hook up the empty lines and 1/4 filled either the dry new or the existing master cylinder and push all the externally cleaned off pistons fluid filled bores back in to bottoming out. It works better on the center stand with the steering turned slightly left so the air goes upward as it travels thru the master cylinder bore, then up-n-out, bubbling thru the partially filled reservoir fluid. On each caliper, push the pistons back slowly, watching for when the air bubble stream turns into a liquid stream, then STOP. Go to the other caliper and do the same thing. Give the front brake lever a dozen small 1/2 inch travel squeezes, just beyond clicking the brake micro-switches. With the steering turned left, watch as a few very tiny bubbles come up-n-out the tiny bleed-back hole. Next, push all the caliper pistons in all the way, watching that the reservoir does not overfill. Since all the air has been removed from the system, you now have a completely bled brake system. Done properly on a system with clean/new fluid will need no bleeding at all. Remember that procedure the next time you change to new brake lines".