I'm popping this question in here as the 7 series questions tend to get no attention; plus this is the same brake system as all other models.

I just bought back my 2000 E38 728i Sport.

It always had a soft brake pedal and 3 years on, its still the same. First 2/3 of pedal travel and basically nothing happens.
So I swapped out the master cylinder last week as I thought I might have damaged it years back, popped in a TRW one.

I pressure bled the whole system when finished and still the same - the first 2/3 of pedal travel is extremely soft and light.

So then did the 2 man bleeding system, had him work the pedal whilst i cracked and tightened the bleed valve. No difference.
I've activated the ABS pump in DIS, no difference.
I've activated the DSC pump too, no difference.

I then pressure bled the whole system again, still no difference. I see no fluid leaks or balooning lines, no evidence of bleeder leaks or brake line joiner leaks.

What in the world can cause this?

Only just now, have I spotted this when the brake pedal is pressed, see the video below:



Is this a normal sound? The air/fluid squelching sound is definitely coming from the ABS module area.

I've also read a report of a bad booster being pressurised before the pedal is even pressed resulting in a soft pedal, thoughts?