I have a 97 f-150. The ABS light is on, the pedal is soft and you need to push hard. If I push the pedal down without the engine running and hold, then start the truck while still holding the pedal down, the ABS light goes out. When I release the brake pedal the light comes back on. I just changed the master cylinder and bled all the lines. Could I have a bad caliper?

 

Did you bench bleed the master cylinder before installing?

 

Check the calipers definetely, check also the rears. I would assume you have drums back there, could be a wheel cylinder or 2 gone bad. Is your truck 4w ABS? Alot of times it's ABS in the rear only.

 

Sounds like you still have air in the system