I did a little research today and took apart one of my E4 levers and took a few images.
- I am impressed with how good of quality and how good the CNC machining of the housing looks.
- The internals match up well with generic cross sections of lever hydraulic cross sections one can find on the web. (No weird or unique design features. - About what I expected to find.)
I believe that I might have discovered why the hydraulic assembly could be difficult to get all of the bubbles out.
In the second and third attached images, I focused on what appears to be almost a bladder, or some sort of flexible pressure equalization/control insert. When I took my assembly apart, the indented area of the insert was facing downward. I think that this indentation, when oriented horizontally, could trap air and not allow the air to escape. These bubbles could relocate from where they are trapped into another area of the reservoir when the bike is oriented in a direction that the bubbles would move to another area in the reservoir. If the air bubble migrates to the small hole drilled between the reservoir and piston assembly, then air could directly be sucked into the piston area. (Perhaps why, a good working brake would get a spongy lever if the bike is hung on a wall, or flipped upside down for a period of time.) This could also help explain when I bleed the brake assembly off the bike versus on the bike, I was able to get a firm feel on the lever very quickly becasue I was rotating the assembly 360 degrees as I pumped the lever.
- This may be reaching a bit, but to me it is one possible explanation.
When I reinstalled the bladder thingy, I rotated it so that the indentations are vertically oriented. When I eventually try to put this lever assembly back in service, I'll find out this works, or not.