At the brake master, open the bleed nipple and push the bike:
a. Caliper is no longer in pressure, bike is easy to roll.
b. With nipple still loose, pull lever in... If the lever does not move, it's a stuck master piston.
c. Calipers are still stuck with no pressure at the line w/nipple still open, then it's s stuck caliper with the lever now moving with the open nipple.
See the combo moves with a nipple release no matter at the master or at the caliper?
In parentheses, the theory goes like this: The quad ring has 4 flat sides. Statically, the quad ring looks like this (I I), meaning it's squared without pressure in its groove. Apply pressure, the piston moves against the pad, pad against the disc and the quad is now (/ /) pushed out of the groove kind of. Release the lever, the quad has memory and moves back to square (I I) again. This pulls the piston back, away from the pad, then no longer against the disc is the pad.
Water is heavier than oil so the bubbles made by heat; what is in the bubble is oxygen, right? So this water finds the lowest point at the caliper and sits under the quad ring where the groove is. The water turns to crystal kind of growth between the quad and groove. This forces the quad to squeeze the piston is one, and secondly, the quad no longer can be square in its groove but locks the piston from moving back, via help of the quad moving back to static memory, remember.
However, with a locked master lever, that master's piston should act like it's stuck and locked down the throat of the bore some. This would cause the lever to be very sloppy by the master's piston being that far forward in the bore. Kind of makes me think it's a stuck master not returning, to a stuck master's piston at the start point... being, you did not mention how the lever is sloppy before it hits the piston to move it down the bore hole...
or did you? [edit on the reread]
Say if you break the nipple loose at the caliper, this tests the lines down to the caliper. No balloon between line to stop flow from returning. Break at the master and does not move the piston, then it's the master.
* Last updated by: Hub on 5/27/2021 @ 8:43 PM *
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