I started with the LR, then RR, then RF, then finally LF. I got the air out of each one until I hit the LF. It just spews bubbles, and no matter how many times I pump the brake, the bubbles/air aren't reduced. I then go back to the LR and follow the sequence again, finding that each line has some air in it (even though I previously got it out).

I replaced the front calipers a few years ago (Autozone). does this sound like a malfunctioning caliper?