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Rear Brake losing pressure..

3621 Views 5 Replies 4 Participants Last post by  Stam101
I have tried everything but my rear brake seems to lose pressure after I use 3-4 times from a relatively high speed. By losing pressure I mean I end up without rear brake at all. Bleeding seems to work for a while but it only lasts 3-4 brakes!
I changed the line but still no improvement.
Would that seem like a master cylinder problem to you?
Should I change the master cylinder?
If not what else do you recommend I should try?
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do you appear to be leaking fluid from anywhere? or does the level of fluid seem to be changing in the reservoir?
At the end of every ride, when I end up with no braking power, there is some fluid leaking from the top of the reservoir. Does this tell you something?
it is too full

i would drain it and then rebleed and try it again
it is too full

i would drain it and then rebleed and try it again

Something to consider is brake fluid will expand when it gets hot. Your brake fluid may be getting hot after using it a few times and if your resevoir is too full the fluid won't have anywhere to go and will push on your brake pads. It might be doing this while you're riding causing the brake to drag and fade away to nothing. You need an air space in the resevoir to keep this from happening. If you've been dragging the back brake because of this then you should check your pads and rotor to make sure nothings glazed over by now.
Thanks for the tip fellas, but this is not the case.
That was my first thought. I finally replaced the rear master cylinder with one from another model and everything is working great. Seems like the OEM one was faulty from the beginning.
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