There's a number of possibilities. If the pedal swings freely, something has become disconnected under the dash. Ford had a big problem with that some years ago, but otherwise that is very uncommon. Brake pedals are designed with preventing that in mind.
More commonly there's a leak in one of the hydraulic circuits. There is always a second system that should give you some brakes. It won't be much, but it's extremely rare to lose all of the brakes. The first thing is to check the brake fluid level. When checking, and especially when adding, be absolutely certain to not get the slightest hint of petroleum product like engine oil, transmission fluid, or power steering fluid in there. Doing so will create a REAL expensive repair bill.
If the fluid is empty, there's a leak somewhere and it shouldn't be too hard to identify where. If the level is real low but not empty, suspect the front brake pads are in need of replacement. If they were grinding metal-on-metal and ignored for a while, a piston can fall out of the brake caliper leading to loss of brake fluid.
Never fill the master cylinder reservoir unless a brake job was just completed. To replace the front pads, the pistons have to be pushed back into the calipers to make room for them. Doing that pushes a lot of brake fluid back up to the reservoir where it will overflow and make a mess if someone filled it previously.
To provide a better suggestion of the cause of the problem, you have to provide some details or history of anything you observed that led up to this.
Thursday, September 18th, 2014 AT 11:09 PM