Replaced a brake line on a 2003 f150. It's the line that runs from the driver's side rear to the front and runs along the frame. Whole thing was just rotten. After i replaced the line and bleed the brakes I still have no pedal resistance. Goes straight to the floor. As a side note because I never saw it this bad before. the brake fluid that was coming out during the bleeding was so black it separated itself from my clean brake fluid in the bottle. Should I consider replacing the brake master cylinder and re-bleeding the system or have any other ideas? I did look at the other lines and none seem to be leaking. It appears that someone before me replaced the brake lines around the rear differential but I don't think the system was bleed because these bleeder screws were tighter than a hookers spandex!
Check over your install and check for leaks. Then bleed the brakes again. If the problem persits, look into the booster/master cylinder.
You may or may not need a scantool to activate the ABS to bleed the ABS module.
Yes, I would consider replacing the master cylinder and refilling the system with brand new brake fluid, especially since you say the fluid looks black.
