I ordered a pair of metal plugs (M12x1.0) for the master cylinder so that way I could do a quick test without having to remove it from the car just yet. Removing the fluid lines from the MC and inserting in the plugs, I decided to go about testing the brake pedal feel in two ways:
With the car switched off
Switching the car on, letting it run for about 5-10 seconds before turning it off.
Testing the brake pedal with the MC plugged and the car switched off produced a tight pedal - though I'm unsure of how tight the pedal should feel (comments/advice would be helpful here). Furthermore, unlike when I had the lines hooked up normally to the MC where the pedal could build pressure via the brake booster and become hard as a rock, it now maintains some level of stiffness, but still has a bit of slop and doesn't build pressure at all. What does this mean?
Onto the test with the car turned on...the pedal was as squishy as ever (would still rise back up, but the same audible air sound and squishiness I've been experiencing throughout this bleed job). Again, it wouldn't pump up to pressure either. Same when I turned the car off, still wouldn't pump up to pressure like it usually did before plugging the MC.
I'd like to point out that in both conditions, the brake pedal didn't "drop" under its own weight, or fall to the floor after applying a set pressure with my foot. The main issue is that it just failed to build any pressure while testing the MC.
Would love to hear any comments/thoughts/feedback/advice etc.