The verdict is still out on the master cylinder, maybe it is defective. My front caliper rebuild could be faulty or the air is just being a real pain.

Do you recommend opening both rear bleed screws simultaneously since there is one line running to the back that T's and maybe possibly elevating the rear too?

Brake pedal doesn't like to pump up firm and whenever you get a little pressure, it sinks immediately to the floor. The car will stop with the pedal all the way down. Also, the flow of fluid at the bleeders was weak with the pumping method.

I used the pressure bleeder and ran all the bubbles out at each end, keeping the resovoir completely topped up. No luck.

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63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6