When I press the brake pedal on my 69 f250 I can hear air escape. The brakes still work, I don't know why it's doing that. My f250 has a brake booster, not sure if it maybe needs a new one? Any ideas?

 

Yep. That's it. That's what happens when the rubber diaphragm inside the booster goes bad. It might have been the master cylnder leaking some brake fluid inside the booster that made it go out. Before buying anything check the back side of the master cylinder. Unbolt it from the booster and gently pull it forward. Just enough where you can get a finger in there to check the back side of the M/C for leaking brake fluid. If it is leaking buy both parts. There are various sellers that sell a M/C and booster combo unit.