On Monday, April 8, 2019 at 5:33:27 PM UTC-7, James wrote:
The GLW has Shimano hydraulic disc brakes on her urban commuter/touring
bike.

Recently the front brake system degraded to the point that the lever
could easily be pulled all the way to the bars. Not good. I bought a
bleed kit and Shimano brake oil for $50. I bled both front and back
brakes as instructed by Shimano. The front brakes worked again as new.

The front brake started making horrid squealing noises. I'm not certain
if this started before or only after I bled the brakes.

However, I noticed the hose from the front brake caliper was damp with
oil near the lever. I suspect the hose connection to the lever has
leaked. Perhaps this is why the system needed bleeding in the first
place. I tried tightening the nut (that compresses an olive on to the
hose just inside the lever body). I'm not certain I have stopped the
leak though.

I suspect the oil moved down the outside of the hose and on to the disc
and pads, and that is what caused the horrid noise.


My cable actuated disc brakes on my gravel/touring bike are working fine
though.

Probably an accurate diagnosis. If in doubt, clip the end and put in a new barb and olive and reinstall. Also check the calipers to make sure there is no leak at the bleed port or the two halves of the body due to a bad inner seal. I had a leaking bleed port because the port grub screw was not seating due to gunk, probably from manufacturing since this was a new brake. I opened the brake and replaced the inner o-ring and worked with the port and screw -- and I think I got it fixed. And yes, a leak onto your pads will significantly degrade braking and cause your brakes to howl -- as will road crap. Bicycle plumbing! The good part is that a 105 or Ultegra level caliper is relatively cheap and plentiful.

-- Jay Beattie.