Why didn't I stop?
 

Yesterday i had to make a panic stop at an intersection - put lots of foot on the pedal. About 1 second into braking the pedal went to the floor. Got home by using the parking brake - no pumpup on the brake pedal.

Today, inspection show a severely rusted connection on the rear brake line just under the driver's seat, lots of fluid on the connector, lines, and ground.

So, I lost my rear brakes. Why didn't the dual master cylinder give me front brakes?

Now, the master cylinder is low on fluid, the red BRAKE warning light is on, and the amber ABS light is on. I haven't taken anything apart yet.

1998 F150, V6, cruise, 2 wheel drive

You most likely had front brakes. When you get a half system failure it just feels like you pedal is going to the floor. I had it happen once in my Dad's old 85 F150 and it feels for all the world like your foot is on the floor. But you really have some more travel before you bottom out.

A way to check - in your driveway roll slowly and push the pedal as far as it will go... does it stop? If so, you have front brakes. You could also do this by jacking up the front end. If you don't have front brakes, you have another issue to track down.

Sounds like you should replace all the brake lines while you are at it... then you'll be good for another 10+ years.

Sounds like your due for a complete brake overhaul, lines, pads ,rotors, maybe calipers. All of this may not be ?needed? but it will greatly increse your braking power and your saftey when it comes to douch bags pulling out in front of you Good Luck.