Brake bleeding weirdness with and Audi A4 headed to the track

So, I'm going to do my first proper track day with my father in a couple of weeks and I'm looking forward to it. Unfortunately, the car prep is turning out to be frustrating.

The story from the beginning: He has a 2004 Audi A4 that he has taken to the track before. About 3 weeks ago, he replaced the dust boot and O-ring on the front passenger brake cylinder. (He did it just because it was torn, there wasn't any leaking or anything). Do do this, he had to disconnect the caliper from the the brake like and when he finished, he bled just that corner with the help of his neighbor.

Fast forward to yesterday, I was helping him bleed the whole system with new fluid and something weird happened. Both of the driver's side brakes bled fine - putting out a bit of bubbles right at first, and then nothing but clear fluid for about 150mLs which is about when we decided to stop. On the passenger side, however, just as we thought we are almost done with each brake, about 100mL into bleeding it, more big air bubbles came out. We decided to pump more fluid through those brakes and probably went through another 150mL on each brake and what we found is that the bubbles tapered off and stopped coming out at the front but tiny bubbles kept coming out at the rear one.

Does anybody have any idea what might be going on? Also, what would you do if you are in our spot? Should we keep bleeding more fluid through to see if the bubbles will eventually stop? Bleed again in a couple of days? Get the ABS to activate?

One thought we had, is that we had damaged the master cylinder because we had pressed the brake pedal all the way down when we first started bleeding. But when we test it, by applying a steady pressure with the car running, it stays still and doesn't sink. Could it be damaged in a way that lets air in but doesn't sink. Am I making stuff up?

What order did you do the bleeding? You are supposed to go from the farthest cylinder (Rt. Rear unless it's RHD) to the closest (Lt. front). If you don't do this, you can keep moving the same air bubble around the system, never getting it out. Are you 100% sure you didn't run the master cylinder dry?

The Bentley manual said to go Lt. Front ->Rt. Front ->Lt. Rear ->Rt. Rear for some reason so that's what we did. I guess that's probably backwards from shortest to longest...

99% sure on the MC dryness. At least when I was there, we kept it topped up very carefully.

perhaps those small bubbles were due to your bleeder tube not fitting snug on the bleeder screw. that happens sometimes and can be misleading.

when I bleed an ABS car, I typically do what you suggest, ie bleed, then drive to get some ABS activations, then bleed again. that's to be sure clean fluid is in the ABS passages, not to try to get at any air in those passages.

i'd drive it, and if it feels OK, i'd drive it.

Thanks for the responses guys. It drives well so far so I think we'll bleed it again and see what happens.

I would probibly re blead the system after your first session on track just to make sure.