Crazy brake issue... 2005 GMC Denali Yukon.. help?

Can’t wrap my head around this one...

Brand new slotted drilled power stop rotors
Brand been pads
Brand new emergency brake shoes
Full master cylinder reservoir.

Old pads were grinding in rear, swapped parts with new parts the day prior. Drove them, broke the pads and rotors In... stopped good. (40-50 miles) made several stops, brakes felt as they should.

Drove today, made a few stops, everything great... all told had probably 100 miles on the swap, went to hit the brakes and the pedal went to the floor, nothing.. T/C light came on, service brake system, Parking brake light etc.

Was able to “pump” them to get the lights off but it wouldn’t stop.

Got it slowed down via downshifting... stopped for a few minutes, left rear brakes seemed hotter than others (smoking slightly and the wheel was noticeably hotter)

Parked it for a few hours, got in it, brakes felt SOLID. Drove it 50 miles home, NEVER acted up, stopped arguably better than it did before it showed its butt.


Any thoughts?

Fwiw, the brakes NEVER went away, felt spongy etc before or after before this. Lines weren’t cracked open at all during the upgrades.

air in system/boiled/moisture in fluid, just some thoughts, were you being ******* the brakes or just normal cruising?

Extremely leisurely cruising. I TORTURED THEM coming back, 80-20mph aggressive stops repeatedly to see if it would do it Again on the ride home, nothing... stopped like a champ.