So, I have been having problems with my brakes lately. Occasionally when I depress the pedal, the brakes don't fully "bite". Pumping the pedal a time or two gets the pressure back in time (for now). Checking my fluid, I found that its black and the strainer has nasty **** in it. I cleaned the strainer so the question is: Will fresh fluid fix this or is the MC going bad? A mechanic told me the MC was designed for "forever" and shouldn't wear out.

 

When I had this problem and posted up before (minus the gunk/black fluid) the consensus was that it was an internally leaking master cylinder.

 

MC has an o-ring in it as do the brake calipers.
The o-ring deteriorates over time and that's the black mess you see.
Both have similar failure symptoms so check your wheel cylinders for leaks as well as around the MC before just automatically assuming it's your MC.

You will need to do a full flush to all 4 wheels after replacing the faulty part(s) to get the fluid with the black contaminants out.