About a month ago I started to loose my break pedal almost 3/4 down to the floor before it hit solid and even when I did get pedal you had to push hard for it to stop. If you let the truck idle for a while at first you had usually one good pedal before you lost it. Not having the time an being around Christmas I pushed it to the side and continued to drive it, last night I pulled into the driveway and completely lost the pedal, could driving the truck with a bad hydro boost ruin the master cylinder also?

 

I have read that you can test the hydro boost operation by pushing the brake pedal down and holding it there with the engine off, then crank the engine and if the brake pedal comes back up with your foot on it the boost is working properly.
Many folks here have had their high pressure hose at the power steering pump blow out causing total loss of steering and braking.
Check your fluid level in the power steering pump to make sure if is full.

 

I've noticed the pedal come up when the engine does start, but the fluid is full. Does this indicate air in the system?

 

Dude, I can't remember now whether or not you F Series guys have a mechanical vaccum pump as an accessory on the serpentine belt like us 7.3PSD E Series van guys do. But I have had to replace mine twice due to the symptoms you are describing.

 

F series is an electric driven pump for ESOF if eqquiped, and for the heat/AC controls

 

It's a tiny electric one, no break assist with it.

PS pump hose failures are new to me. I see a few threads about it but is it really a common problem?