Brake issue- what happened?

[65Ford]

Driving into work other and day coming to a stop sign the brake pedal goes down to floor after a felt a kind of 'pop'. I pull over to side of road using e-brake, get out look all around but don't see any fluid anywhere. I happened to have Dot3 with me from old leaking clutch master cylinder and top off brake master. Get back in truck pump pedal few times and pressure comes back and from then til now its been alright. I think maybe drivers side caliper was sticking/frozen and 'popped' open? Master cylinder beginning to crap out? Any guesses? Thanks-

 

[Road Angels]

did you check the rear brake backing plates to see if they where fluid soaked ( wheel cylinders.), if a caliper was frozen or sticking the steering would pull to one side as well as the brakes/ rotor would be really hot, was the fluid low before this happen or normal level,?? If the pedal bypassed and went to the floor, if you didnt need a master you will soon, because you push the piston and seal cups into the crap that builds up out side the normal pedal travel, witch is destructive to the seals inside take the time pull your wheels and look at every thing its not worth taking a chance, good luck

 

[65Ford]

Found out what happened just not sure how really. Did front brake job and when I pulled the front pass side tire off and looked at the brake caliper the inside pad had somehow come out and was wedged between the dust shield and rotor. The truck had been pulling to the right recently and maybe the 'pop' was when the pad fell out, not sure but replaced everything on both sides and all's good now. Thanks Road Angles for reply- good suggestions