F150, 2000, problems with brakes

If you step on the brake pedal and hold it down and you feel the pedal going slowly down, that's for sure your Master Cylinder unless you have a brake fluid leak from one of the calipers. If you have a brake fluid leak, you will notice it because you will have to keep on adding fluid to the system. If you notice a change in your RPM when you brake then you may have an air leak from your vacuum to manifold hose.

the condition you have experienced is called brake fade . It occurs when there is insufficient brake pad to adsorb the heat generated buy the changing of the kinetics energy (spinning) into heat energy by the friction of the brake pads on the disc rotors.. It gets to a point where the pads and discs will not take any more heat so when that happens it does not matter how hard you push the pedal there will be no brakes. To prevent this happening again fit new brake pads and fit new disc rotors. If you are going to be doing steep hill work then get a brake pad suitable for hard work. Talk to a brake shop specialist to get the best pads for the job. Another experience that you will have is when the brakes get hot the pedal goes to the floor. This comes from bad brake fluid and happens when the brake fluid absorbs moisture from the air and the boiling point of the fluid is lowered considerably. The oil boils and the water in the oil turns to steam and you get vapour lock in the system and you will loose brakes as you are compressing steam or air.. The fix for that is to ensure that you change your brake fluid every 12 months.

It is most likely you have air in the brake fluid. The first press of the pedal compresses the air and the effect lasts for a little while.
Another cause may be warped (bent) rotors, the pads can be pushed back into the calipers by the off center area of the rotor. This means that the pads have to travel further in order to contact the rotors when you press the pedal.

i think you have overheated the pads so the brakes just seemed to fade with a hard brake pedal but no stopping power ,they might be ok with some use as this will clean up the burnt surface of the pads ,if the disks show no blue colour then your ok and maybe a different grade of brake pads will resolve this problem

Because it is the brakes AND it came on suddenly. GET THE WHOLE SYSTEM CHECKED NOW! Have you checked the condition of the brake pads? Heavily worn pads can affect how far the pedal travels before the brakes bite. Is the pedal spongy? There may also be an air bubble in the system so get a good mechanic to check and bleed the brake lines. If these are OK your looking at getting master cylinders and brake servos checked or replaced.

Did you bleed the lines and master cyl. If you are talking about the flex lines that connect to the caliper, did you make sure that the fluid did not
drain out.

If the master cyl did not empty you will just have to bleed the lines again,
have someone help do do this. If you don't know how, just post it
and someone will get you a nice detailed page of bleeding your lines.

the only thing i can think of as a problem would be brake pad quality. i would get some from the dealer and fit them. if there is chatter going on it can also be caused by low quality rotors or a bad maching job. have them inspected for integrity.

That sounds like the "Porportioning valve" is defective.
You may want to go to your local library and check out a Chilton's, or some other repair manual for the "how to" to fix yourself or take it to a tech you can trust.

pedal goes to floor .... did you change the calipers.... sounds like air in the system

are your rear drums set up? why did you bleed the brakes. when only when you installed new pads?