If pedal sinks with no link the only place i can think of is the piston seal for the front circuit.

I've noticed my pedal will very slowly sink under constant pressure so I'm due for MC rebuild.

New ≠ fixed, you have to follow the symptoms even if it means the brand new part is the likely candidate.

It's very strange to have zero pressure.

If you hit the pedal hard but don't hold to you get resistance? (Suggests weak vs. missing o-ring).

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)