ok i've replaced the master cylinder, booster, calipers, hoses, pads, and rotors on my hatch (stock brake system) and after the car has been driven for a few minutes the pedal gets stiffer and stiffer until there is no play and the calipers start closing and get tighter and tighter until i have to put foot almost all the way in it to keep the car moving..i've bled the brakes 8 times, no air, and am just not sure where to go

 

mabe try adjusting the pedal did it do this be for the master cylinder? Have you checked the rear drums to see if the e brake cables are stuck?

 

if you jack it up is it just one wheel or all the wheels? it might be a brake hose because if they get pinched they can work as a one way check valve.

 

bad valve between the intake and booster