[Zack]

So today a friend and I were bleeding my Hayes Mag. We were doing everything right but it just wasn't working. It felt like there was no pressure in it, for the lever would go all the way back to the bar. So we tried redoing it several times - nothing. On the last time, we were doing everything the same as usual, when suddenly a piston shot out and all the fluid just drained out of it in about 5 seconds. I have no idea how this happened. I managed to pop the piston back into it and it feels secure, but is this brake shot for good? Should I take it to a shop? Or is it time to buy a new one?

 

[Matt D]

Could you desribe the problem more? Use the names on this page:
http://www.hayesdiscbrake.com/pdf/MasterCylinderRebuildEnglish.pdf

If the push rod poped out, you probably need a new MC assembly, but that's just speculation until you tell more.

I imagine you've bled Hayes many times before and had success? Or are you new at this?

 

[spam16v]

i think he's talking about the piston in the calliper. and i havent had one pop out yet. i bleed with the brake on the bike personally with a disc crammed in it.

 

[Zack]

Yeah, the piston in the caliper. I think I figured out the problem was that the cardboard that I had in there was squished too much so there wasn't enough stopping the piston from just being pushed out by the hydraulic force. Next time I'm going to use an old set of pads or something. I hope the brake is okay though...

 

[Matt D]

It's not a big deal then and you should be fine. Just as long as the o-ring is still intact and holding the seal.

I didn't know the piston pops out w/o any pads in there, but then again you shouldn't be pulling the lever w/o pads anyway!