[Fett]

I just got back from a MTB vacation in Durango CO and during the trip, my 03 Magura Louise brakes failed on me and we cannot seem to find the problem. We rebled the brakes twice. One of the guys who was with us is a very experienced bike tech who also is a big Magura fan (Martas) and he could not figure it out.

The brakes would lose the lever pressure as if it had air in the system, but none could be found in the times that they were rebled. Also the brakes would work if you pumped them vigorously for a bit or if you had a big downhill section, you would seem to get the lever back once they got hot, but lever would go back to the bar once they cooled off.

There is no obvious signs of fluid leakage. It has been an problem for a while, but seems to be getting worse to the point that I have almost no front brake now.

Any ideas or suggestions? I am stumped.

 

[The Squeaky Wheel]

I hate to say it, but it sounds like you still have air in the system.

Proper bleeding technique is crucial and it's possible you missed the air.

Check out the cult website if you haven't done so already.

I bleed mine forward & reverse three times. I also purge trapped air from below the reservoir cap before replacing it and I set the pads on the rotor to ensure maximum fluid volume. All this is explained in detail on the cult site.

good luck.

 

[itsdoable]

You should call Magura and describe the problem. If fluid level is not low, and there is no air in the system, it is probably a leak on the inner most o-ring on the master cylinder piston, the mineral oil will seep past the first seal and into the resevoir while you have pressure on the lever. I had this intermitantly on one pair, Magura sent me a new piston right away. Happens when some dirt gets stuck to the o-ring, or the o-ring get a nick.

 

[Pat T.]

Sounds to me like a combination of low fluid and pads are getting to the point of needing replaced. I'd bet if you replaced your pads the and topped off the fluid your problem would go away.

 

[Fett]

Sounds to me like a combination of low fluid and pads are getting to the point of needing replaced. I'd bet if you replaced your pads the and topped off the fluid your problem would go away.

Pads have been replaced in the last month and have little use on them.

I will definitely call Magura to see their thoughts. The condition that itsdoable describes seems to be the most likely culprit as now that I have the brake off, I can see leakage around the master cylinder, which could be introducing air into the system.

I agree that it acts like there is air in the system or low fluid, but trying to figure out where it is coming from is driving me crazy, but a leak in the piston would seem to explain it. It is not alot of fluid, but I am guessing it does not take alot to make it feel bad.