Brake problem

95 C1500 Ext Cab 2wd auto. I just recently when i push my brake pedal it would be hard to press at first then go to the floor, just like when bleeding the brakes. Did this for 1½ days then saturday night they became hard to press and would not go to the floor and would not stop the truck, had to put it in nutral and use ebrake and regular brakes.

~Brake Pedal wont compress
~Air leaking sound when brake pedal is pressed(stops when released)
~Master cylinder fluid low but not gone
~no visable fluid leaking

Anyone got any ideas, im thinking air in the lines or master cylinders gone out

Air leaking sound is power brake booster. Needs to be replaced. As for pedal going to the floor, sounds like you also need a master cylinder. Seals on piston are shot.

thanks man

Check for a blocked vacuum check valve first