imsolidstate

I'm having an issue with the brakes on my 2008 Q7 V8. The last couple days I've smelled a burning smell when I got home, and tracked it down to the front left and rear right brakes. They were really hot while the other two were cold. Yesterday the pedal started getting soft. I figured I'd start with a pad/rotor inspection and fluid flush, so I got the right rear wheel off. The pads and rotors look pretty much new. So I started the brake flush. First pump I got some fluid, second pump a little less fluid, third pump no fluid. I haven't got anything out of it since then. I loosened the line that goes to the caliper with pressure on the brake and no fluid there either. The pedal is not going down either so nothing is moving. Is there something special about this vehicle's brake system I don't know about? Thanks.