Atv Rear Brake Problem

I'm sorry if this is the wrong thread but i got a brake problem on my 09 wolverine 450. We checked the master cylinder and bled them almost every way possible, vacuum, mash the pedal, letting it sit, and gravity bleeding (hold a funnel of fluid going into the bleeder higher the the reservoir). My dad even bought a new brake line and that didn't even work. The only thing that worked was holding the caliper in the air until we bolted it.
how this happen is i was riding this pile and my rear...

Atv Rear Brake Problem