Brakes are locking up on me. PLEASE HELP

[shotgunhunter4]

I have already searched and searched and because i search so much I have close to no posts at all. Heres my situation, about a year ago I bought a 95 240sx with a blown engine off here and finally about a month ago was finally able to get it to run. I knew i would have to change the brakes so thats what i did. I changed all the pads (I have all disc brakes) and turned the rotors. I then took if for a test drive about about 5 mins into it, I noticed i wasnt coasting very far and it was taking much more gas to keep the car moving. By the time I got home they were smoking like crazy. I then rebuilt all of the calipers and lubed the pins that slide the caliper on and off the rotor and made sure they were working well. I then took it out for another test drive and about 5 min later the same thing started to happen again. So I went oh here to figure out what the problem could be and I guess it could be a bad vacum line from the brake booster. but my question is how do I check the brake booster and master cylinder? What do i look for when inspecting the lines? Could a slight crack in one of the hard lines from the master cylinder do this? What else could this be from, am I missing anything? I really want to get this car up and running. Thank you for anything and everything.