I have a 97 F-150. I recently changed the brake fluid; however, I was only able to bleed the front brakes. I followed the standard procedure of loosening the bleeder bolt with a hose over the bleeder. Then had someone press the brake. When I did the front bleeders, the brake went to the floor and brake fluid came out. When I did the back ones, the brake would only go half way down and hardly anything came out.

P.S. I made sure the brake fluid reservoir was never empty

Any possible explanations would be appreciated

 

Welcome to the forum!
As far as brake fluid coming out of the rear at a reduced rate, I'm not sure but someone else may chime in on this: Brake proportioning valve in the plumbing somewhere-possibly? More fluid is going to go to your front brakes for better stopping anyway.
As far as bleeding brakes with the pedal: I would just gravity bleed the brakes. that you can do yourself in an hour-hour 1/2. Start with the furthest wheel away from the master cyl, one wheel at a time. crack the bleeder screw, with the tubing over the screw and allow to drain until it flows clear.
I use a piece of clear tubing to tell when the brake fluid is coming out clear.
I also keep the cap loose on the master cyl. reservoir which i cover with a clean rag as well. and keep the fluid full in there during the whole process.
Hope this helps.

 

take the bleeder screw out and see if it is blocked with dirt or something