Rear brake bleed issues

For the life of me I can’t pump nor suction brake fluid through the nipples on the back brakes on the backing plate. It comes through the block, comes through the lines to the piston, but won’t come through the piston. What’s up with that? My brakes are super firm, but I’m not even sure the rear brakes are engaging, though all the parts seem to be moving. Anyone have any theories as to why and what to do about it?

 

Going by memory, I had the same problem. Turned out the proportioning valve needed bled 1st.

 

Awesome. That would make a ton of sense. Thank you!

 

If your truck has a lift make sure the LSBPV actuator rod bracket has had an extension added the same length that the lift is in height.