Isuzu Repair: isuzu brake problem, caliper pistons, sensor box

Question
i have an isuzu 1998 kb 2.8dt pick up. i live in south africa. when i travel i loose pressure in my brakes,ie the peddle goes to the floor. after 2 pumps the pressure is back for initially 5km now only a couple 100 metres. i have bled the system 3 times, replaced the master cylinder and have no holes in the line. the fluid level does not drop. it does not have a computer in the vehicle so any help would be appreciated.there is a load sensor box above the diff which is about all i havnt touched- dont know much about this box which is attached to the bin and a arm runs to the diff.

regards steven

Answer
Well Steven. A low pedal usually means there is air entering somewhere in the lines, so i would have your lines leak tested. Also your pads could be the problem, check to make sure their not worn down. Or you could have bad caliper pistons/seals, i would definately check this as well. tell me if this helps. I hope it does! have a great day steven. Send me some pics from africa!