Was the master cylinder bench bled prior to installation and were the brake properly bled upon completion of master cylinder and hose replacements?
Make sure when bleeding the brakes that you keep the resevoir topped up, other wise the rear chamber will run dry and you'll do nothing but pump air to the rear brakes.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.