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Trying to bleed a Magura Louise brake, as per these instructions:
I'm stuck at the point where I squeeze fluid from the bottom syringe to the top syringe. The fluid won't flow. I've removed the hose at the lever to check that for blockages and that is all fine, so the issue seems to be with the lever.
The lever is working in that squeezing it moves fluid into the bottom syringe and releasing it draws the same fluid back into the system, but it's not letting fluid through when being bled.
Any ideas before I dismantle the lever (if I can find a small enough torx bit)?
Cheers
Are you squeezing hard enough? I find the seals in syringes swell up and almost sieze them solid, and there's a lot more mechanical/hydraulic advantage squeezing the lever Vs the syringe.
Quick test would be to fill the resevoir, pump the lever whilst pulling up on the syringe gently, the level in the resevoir should drop as fluid gets pumped through the system.
Otherwise the only explanation I can come up with is the lever isn't returning far enough to open the port at the bottom of the resevoir and allow the fluid to move from one to the other.
Ha ha, definitely not a problem with squeezing hard enough. It's this issue that led me to exploding a piston out of the calliper by accident. I'm using a brand-new syringe and I've done three brakes already the same way, so I know that the pressure isn't the problem.
I've tried pumping fluid through from top to bottom with the lever, that didn't work either, though I'm going to try it again just to make sure.
I can't see how the lever isn't returning far enough, I've checked that too. The symptoms are the same though, so maybe there's a problem with the valve that's having the same effect.
I've taken the lid off the reservoir and removed the bladder. The bleeding process is pushing fluid into the reservoir, but not out of the bleed port.
Looks like it's the valve that is either not opening far enough or the bleed port is blocked somehow.
I've removed the lever, does anyone know how to remove the piston assembly from the master cylinder?
I have 2 set of magura louise, one has a bleed port on the res cap, the other doesn't. I'm used to bleeding the brakes by taking the res cap off, so do it that way on both sets.
Level the lever, remove res cap, level it perfectly using fluid as a guide and bleed away. Put lots of rags around the lever and pop the res cap back on so excess fluid comes over the top and into rags.
I've taken the lid off the reservoir and removed the bladder.
this confused me. Is the little bladder/membrane not attached to the res cap? It should be.
Hello, thanks for your input, yes the membrane is attached to the reservoir cap, but it's a separate part, they're only held together by brake fluid and the three bolts sticking through them. I wrote that so it was clear I'd removed both.
I read that the piston assembly doesn't really come out, that if you take it out it won't go back in without breaking it. I'm not sure that is entirely true as Magura put it together at some point without breaking it, but I couldn't find any evidence that it was possible or how to do it.
So my next thought was that I should first see if it can be bled without using the bleed port, so I'll give your suggestion a whirl....