Hey how are you doing? My car has been sitting for months now and I took it for a drive today. The car starts right away and the clutch is fine, however, when I press the brakes, it sinks to the floor unless I keep pumping it. You think the brake master is taking a crap on me? I don't think thats a brake booster problem.

The problem is you have air in your line it needs to be bleed.

Thats what happened to me, Took it out in April from being in the garage 2 months, didn't have any fluid, filled reservoir, bled them, and then It got to the point where I had to get the new Master cylinder, because I was having to top my reservoir up daily. After the new part All my problems were gone ( Break related )

There might be a slow leak on one of your lines or calipers.

My rear left caliper was slowly leaking. I had to top up brake fluid every couple of weeks. I neglected it once and got air in the system, pedal went to the floor. I found the problem and changed the rear caliper.

Fine ever since.

Make sure you check for leaks before forking out money on a master cylinder.