I spent most of the day today from early morning to early evening at Guy’s hangar in our attempt to get his left brake line filled with brake fluid.  The first system we tried yesterday, from Aircraft Spruce, was a gravity system that just did not work whether the nose was up or down.  No Joy.

The next system that Guy bought locally was a vacuum system, which while it did get more brake fluid into the system, it still didn’t fill the lines.  We fiddled with that for a good couple hours this morning trying to make it work, before again calling No Joy on that one as well.

Luckily, I got some good actionable intel from my buddy Dave Berenholtz back in 2022, after which I bought a pressurized brake fill/bleed unit off Amazon… which I brought with me to Guy’s hangar, having never opened it previously.  So after a couple false but promising starts with my brake bleeder, we went to Lowe’s to pick up some fittings and an on/off valve.

My upgrade mods to my pressure system worked a treat and after days of failed attempts to fill this damn brake line (including ensuring the lines were not obstructed) the new setup filled the entire line very quickly: in less than a minute (@ ~17 psi).

Now, while investigating and researching brake bleeding issues and techniques on the COBA forum, I ran across some more good intel regarding brake line runs from wheel caliper to master cylinder, from Marc Zeitlin and a couple of others.  The one big rule of thumb I took away from these discussions was DO NOT have any major loops, peaks or even valleys if you can avoid them.

Not being a “brakes guy,” I didn’t realize the configuration of the brake lines was so critical since I figured it was all just internal pressure anyway.  But the main critical issue is to always be able to bleed the brake lines well and remove any air bubbles, which any loops or high points makes a lot more difficult, and provides a big potential point where air bubbles can get trapped.

I didn’t follow these guidelines (that I never saw previously) when I made “service loops” in my brake line runs in the hell hole.  I ran about a 6″ high loop up the aft side of the GIB seat just in case I ever needed to reconfigure or have extra aluminum brake line to work with.  I’ll get in there and remedy this before first flight.

Another issue noted by Marc Z. was to NOT use the 1/4″ tubing that is standard on Matco master cylinders, but rather smaller diameter 3/16″ or 1/8″ tubing, the latter being preferable.  Why Matco goes with a larger tubing as standard is something I’ll have to investigate.  But Marc’s claim was backed up by a number of other online non-canard posts, with a few pointing to using 1/8″ tubing from brake caliper to master cylinder, and then 3/16″ tubing from master cylinder to the clear external reservoir.  This is what I am going with as my new configuration, so I pulled the trigger on new fittings from Aircraft Spruce.

In related news, Guy is a couple inches taller than me, and when he climbed into his bird to manipulate the brake pedals in the normal sitting position, I took note of where his feet were located inside the nose.  I grabbed a shot of his internal nose (short style) configuration as a guide to when I do my final pedal installs/rudder cable rigging.

The bottom line is that although I spent a good bit of precious time helping Guy on his brake issues, I learned some critical lessons regarding my brake system, including how to use my pressurized brake filler/bleeder unit… replete with spiffy new mods.

Back in my shop, being a bit worn out from the day’s shenanigans in yet another crazy hot workspace (Guy’s hangar), I wanted to get at least the bottom right wing micro’d up… which I did, including the bottom of the right aileron as well.

And with that, I called it a night.