For the last year or so, I have been having to add brake fluid to the master cylinder every couple of months. I get in and drive it today and the pedal goes almost all the way to the floor. I can't find any leaks around the rear cylinders or in the lines, front or rear or at the master cylinder itself. I can't see fluid leaking anywhere. I figure the master cylinder is leaking somewhere internally. Does that mean the master cylinder needs to be replaced? If so, would it be worth it to do the F350 upgrade? Would just the booster and master cylinder work or would I have to spend more $$$$$ for other parts?