Problematic S6 rear brakes

[Jesse_Boyer]

I have a weird situation happening on my recently swapped 02 S6. The rear brakes aren't working as far as I can tell. Normally after a car sits for a while, the rotors get corroded and it takes a few miles for the pads to clean off the rotors. These were especially bad as the car sat for at least 18-months without moving much. The fronts have cleaned up nicely, but the rear rotors look awful. There is almost no way they're actually doing any braking whatsoever based on how little they've cle

After removing the brake master cylinder, I pushed a ton of new fluid into the system and consider it to be fresh and free of air. The pedal feels firm when it should, so I don't think we're having issues there. It stops well despite the rear brakes looking like they haven't worked in the last 600 miles (miles since swap.)

Any chance both rear calipers are stuck? Is there something I should do to the ABS or brake master cylinder to make sure the rear brakes aren't causing issues?

[G0to60]

Does your parking brake work? That will tell you if the rear caliper were stuck.

[Jesse_Boyer]

Good point, I should have added that. Hand brake works ok-ish

[stp359]

Take off the rear caliper and take a look at the guide pins. They are probably seized. It's a common problem.

[julex]

^^ which means that inside of rotor is probably scrubbed and squeky clean since that side get a push from brake cylinder even if pins are frozen solid.

[Jesse_Boyer]

Found one very bound-up guide pin and one that didn't move very freely. Fixed those and I do think it brakes better than before.