front pass. side brakes lock up

[gmc1971harwich]

i was driving my truck last week and the wheel kept pulling to the right when i hit the brakes so i thought it was the caliper, so i replaced it, and bled the brakes and it was the same. still locks up, stays that way until i crack the bleeder,, then it frees up till i hit the brakes again. my friend told me its probably the rubber line that connects to the caliper collapsing which locks in the line pressure to the brakes. he checked the wheel bearings and there fine, no play and wheel spins freely when its jacked up and pressure is cracked at the bleeder. do u guys think its the rubber hose or could it be something else?