Brake issues, possibly air in the brake lines?

[Dohnut]

Car is 2011 B7 Passat Tech Sport 2.0 TDi 170 50k miles.

Brakes started to feel a bit weak just after new year so got my mate (who is an ex BMW tech) to take a look, we had limited time so we cleaned the discs and pads with a wire brush, bit of sandpaper and brake cleaner and did a full fluid change with a plan to replace the discs and pads all round when we got back from our trip. Due to my stupidity and the yellow filter in the reservoir making it look like the level was good, it did drop a bit low. Probably added a good 200-250ml (guesstimate) but we did more bleeding until no air was coming out.

Brakes seemed better but the pedal had a weird behaviour where say you are driving along and want to put about 20% braking force on just to slow a little, the pedal would go firm as expected and you would feel a gentle braking as expected but it seemed like the pressure would drop, you could feel the pedal sink under your feet with fading braking feel. Release and brake at the same 20% or more again 2-3 times then there was instant and consistent braking and the pedal would stay firm. Basically if you didn't brake for 30 seconds or more, you would need to repeat the process the be able to brake which was unusable.

We replaced the discs and pads all around yesterday with genuine Bosch parts (not cheap rubbish) but again due to limited time we didn't have time to bleed again with a full fluid change. We plan to do this in a few days time, but wondered if anyone had seen this before if it would point to another issue apart from air/fluid? The old discs and pads were in a bad state for the age of the car and the rear had different style of pads on them (thanks Arnold Clark!), quite surprising. The braking is now fantastic and although much improved, there is still a slight fade and pumping required to get the full power of the brakes although I haven't been braking hard until the pads have bedded in.

Couple of questions:
1) He used the standard routine of bleeding the furthest away point being the rear right (passanger side), rear left, front right, front left but doing some reading today I see guides saying start with the front left first, then front right, rear left, rear right and do them 5 times!? Is there something specific to this car which requires a certain sequence?
2) VAGCOM VCDS arrived after we had done the initial fluid change/bleed but still plan to do the ABS pump cycle, does anyone have step by step instructions for this?

Thanks for your time!
-MM

[vwcabriolet1971]

Were the brakes pressure bled ?

[Dohnut]

We used the basic pump the pedal technique and topping up the reservoir, but I did let the level go low at one point, but still thought all the air was out. It's only cos the brakes had suddenly got poor in the couple of days before that we doubt air was introduced or if it was, it was purged. No leaks anywhere we can see.

[vwcabriolet1971]

You need to pressure bleed & renew the hyd. oil for the complete brake hydraulic system.

[Europa25]

I had a B6 for 4 years, brakes were great.
I got this B7 7 months ago, brakes never felt sharp to be honest.
It's DSG, and just recently, the brake pedal firmed up so much when off, it was hard to push it down hard enough to trigger ignition (when vacuum would restore).
I took it in and they replaced the servo (6 hour job), which seems to have cured both issues.
It occasionally firms up a bit, but definitely improved and brakes good again.