Brake issue

Hi I had a problem with my drivers side rear caliper seizing on and off I decided to replace all 4  brake calipers and pads as they were all in bad condition I also replaced some of the hoses.I have bled the system a number of times now the system holds pressure with no air but the brake pedal goes straight to the floor does anyone know why this could be the case?

You don't have to double post.  
It will get answered. I answered in the Help one.