Installed the brake system and, in a fit of optimism, safety wired the bolts
retaining the caliper before bleeding the brake.
The directions to insert the brake fluid using a squeeze bottle via the bleed
screw didn't work out - apparently, the hole from the bleed screw to the
caliper cylinder was nearly blocked by the retracted cylinder. This allowed
air to pass slowly but the opening was so small that it was impractical to
fill the system this way. I tried filling the system in place from the
master cylinder and then found that the bleed screw would not seal when
pressure was applied by actuating the brake. Examination showed that the
small hole which the point on the bleed screw should fill was not centered in
the threaded hole so the point could not seal it shut. Europa replaced the
caliper unit however the hole in the second unit was better but not quite
centered either - it took several tries and considerable torque to get it to
seal.
TFE paste was used initially on the hose fittings which screw into the
caliper and master cylinder. These fittings must be oriented to allow
dressing the hose properly so could not be tightened to stop a leak which
allowed fluid to weep out around the threads. Teflon tape was substituted on
these fittings to provide a seal while orienting the fitting properly.
Given that it was not possible to insert fluid via the bleed screw, a
different approach was taken: the brake system was removed intact for
filling. It was surprisingly easy to remove/install the brake system as a
unit, i.e. with the caliper and master cylinder connected by the hydraulic
tubing. The master cylinder was then clamped in a vise for filling. The
caliper was assembled with two tongue depressors between the linings to
prevent the piston from coming out too far. Fluid was added a little at a
time via the master cylinder while the caliper assembly was held higher than
the master cylinder so air would find its way to the bleed screw - the master
cylinder must have its opening re-sealed prior to pulling the handle to avoid
fluid being ejected. Each time the handle moved full stroke the stopper was
removed and more fluid added; eventually the handle ceased to move full
stroke and the bleed screw was used to remove air. The caliper piston was
retracted with a C clamp, removing fluid from the masted cylinder as needed.
A syringe plus a short piece of tubing was used to insert and remove brake
fluid a couple of cc's at a time as needed.
Once the brake system was filled, it was installed intact. The master
cylinder can be manuevered around to the stbd side of the LG frame and then
pulled back over the top of the frame. (A large rubber band through the hole
in the brake handle will allow it to be pushed up through the slot and then
the rubber band will keep it from sliding back while you gain access from the
cockpit.) Installation time was under 10 minutes.
This approach works on the Mark 1, don't know whether it applies to the XS.
In retrospect, it would make sense for Mark 1 builders to assemble and fill
the brake system well before it's needed since this will facilitate checking
for leaks as well as possible problems with the bleed screw.
John A044 Newtown, CT
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