Jun of 2016 brakes started going all the way to the floor while backing out of the garage when engine was first started. vehicle would roll down driveway and brakes would not stop it until pumped. took vehicle to ford and they could not duplicate. they finally replaced the master cylinder and the problem stopped for 10 months. now the problem is back and they cannot duplicate again. has happened twice this time backing out of garage (less than 5 mph). car has had a full brake job, no leaks, and has 74k miles.