why does my dads breaks on his truck not work when hes changed the master cylinder and nearly everything else on it to his truck is a mitsibuishi perjero if that helps with any answers

Did u bleed all the brakes of air u got in it now? U have to bleed system get air out

yes we`ve done everything we can but its still doing it so we don't know what to do next it breaks my dads heart especially as he is a full on mechanic and he still cant find the problem

Did u check for ANY leaks along whole system. U'll never get brakes with a small leak. Did u rule out u may have bad master cylinder. Ur dads a full time auto mechanic? Wat does he think?

yes we did that but it still does it and my dad has no idea why its playing up after all the years of being a mechanic its so stupid and ignorant so we don't know what to do know its a pain in the ass

did he bench bleed master cylinder before puting it in?after this, if condition still ther... you should have 2 lines attached to master cylinder, disconnect one and put a bolt into master cylinder to seal off this line and see if the still attached line works under pressure. Rebleed the line you took off than do the same for other line. you'll have to a lot of bleeding but i think this could isolate a line (front or back) thats giving u trouble. what about ABS control unit? Just some ideas that might help, I hope!

we did this and its still doing it so we don't know whats wrong with it thanks for ur help

U gotta b kiddin! There has to b a leak, air being drawn in and out. All this time and energy! Take it to a good mechanic then. Let us know wat it was if u find it.