Let's try a little theory:
1. Quad-Ring - This is a square type oring that has memory, wrinkles upon pressure and returns to square upon release [of pressure].
2. Caliper's Groove - Here is where the quad's OD sits and this groove has to be perfectly clean to have the quad return to memory.
3. Caliper's Piston - The ID of the quad-ring circles the piston and is pulled back via memory going back to square, meaning, the piston is pulled away from the pad upon release [of pressure].
Liquid Theory:
a. Water is heavier than oil so when the DOT heats up, boils the oil, what is inside that bubble? Oxygen, i.e., water/moisture/fog/you cannot remove the chemical from the air say.
b. The water settles under the quad-ring and begins to crystallize. This is now a solid and applies pressure to the quad's OD in the groove so the quad no longer can return back to square.
c. The piston is now stuck in position, begins to rub a pad down, shows how the other pad has more meat left, because that cleaner groove shows it can return the quad back to square.
Groove Cleaning:
I. I dip only metal parts in vinegar, sans any rubber that will cause swelling.
II. I never sand the machined or finished parts, so paper towels are only used on those surfaces.
III. I concentrate on cleaning the groove so the sun is my friend and brake clean shows what crystal still remains in the groove.
Bleeding:
You might as well look at the master as gathering water from a well. You are constantly pulling/pushing on the well's pump lever so why not do the same with the master's lever/pedal. Priming the master is the same as installing the line and prime the master, as if the line's banjo end was the end of the master [so you now killed two birds] at the pump. The nipple action is one move only. It's opened when bleeding begins, and closes when the bubbles end. That's the action and I had a pedal the first time I closed the nipple in the vid. The 20/20 said I should have stopped, but showed multi openings at the nipple and once at the master's banjo. But then again, those are the bubble points to finalize, or unless you are familiar with your pedal's pressure, meaning.
I'm going to assume the brake light worked before and it's a pressure type switch. Once you have a pedal the line pressure will push the plunger and trigger the light.
sorry, pain is keeping me from thinking straight today.