2000 f-150 4x4 85,000miles. I was driving slow through a parking lot. Light pressure on brakes, then a pop sound, poss rear. The brake pedal slowly goes to floor. I get to parking spot and check underneath. No signs of any brake fluid. My partner comes over I had him push the brake pedal, While I looked underneath, Nothing, checked master cylinder dry. I got home and inspect brakes lines to back, dry. I have half brake power now seems like more front. Anybody have any ideas what might be problem?

 

You might have blown a seal in the Master Cylinder. Your description sounds more like a brake line, but you say there is no fluid dripping. Is your reservoir level staying constant?

If you blew a seal then the fluid will just push back into the reservoir.

Check again for fluid dripping. If none, I'd replace the master cylinder.

 

I have my truck in for a Brake booster vaccuum line recall, right know

 

Update. This morning I noticed a rattle coming from the read. I pinpointed to driver rear wheel. The inside brake pad broke apart from the metal. The pad is sitting on the dust shield. Now I need to replace the back pads. I haven't taken the wheel off yet, to see if the rotor is damaged. If so I need new rear rotors too. P.O.S bendix pads. Going to buy ford pads.

 

I would recommend hawk pads

 

UPDATE. The driver side pads were frozen to the the slides.Rust. Pad fell apart, due to restricted movement. There is a silver cap on the metal mount. Removed that and clean the metal and the cap. Put back together and pads moved freely. Did both sides. Pad wear was 50% more an the piston side.

 

I installed these all around roughly 25K ago.
No dust whatsoever....no noise....
http://www.tirerack.com/brakes/brake...Lug&perfCode=P