iammacey

Essentially diagnostics.

Some ABS braking systems isolate fluid specific to the ABS module. This fluid isn't flushed through a standard bleed.

You need to run diagnostics and the computer will cycle the ABS system and flush the old fluid and any potential air trapped in the ABS system.

When you pump the brake pedal repeatedly it has no resistance at all? Straight to the floor like it's not building pressure? Same with the car on or off?

​​​​And you've ensured no leaks through any of the bleeder valves or brake lines? You used new washers on the banjo bolts going to the calipers?
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991carreradriver

I just finished an all four caliper rebuild with the same kit from RB. Here are my thoughts on your dilemma:

1. Do you see any BF on the floor?
2. Have you removed each caliper, removed pads and looked for signs of BK leaking from the pistons? If they are wet, it would be coming from an improper piston seal seating.
3. If 1 & 2 above yield no results, then air is in the ABS and needs to be reset with PIWIS. This assumes the Master didn't fail coincidentally

Here is another thought that is probably are not the culprit, but worth a mention:

1. I once did a flush and wasn't paying attention and introduced air into the system. I purchased less expensive fluid (Blue Can OEM) and re-flushed using two quarts. That did the trick and then re-flushed with XRF.
2. When you did the after rebuild flush, did you take care to tap the calipers (with a rubber mallet) to remove any air that adhered to the calipers.

Perimeter

Sounds like air is in teh ABS return circuit and you need to manually open via PIWIS to flush ... or perhaps drive along and hard brake on gravel to activate the ABS and exercise the return circuit