Brake fading

[Willcoc]

Problem with my Dads 05 3500 srw Dmax powered truck. After driving the brakes fad away to almost nothing. Pedal going to floor and not fully returning. Let it sit for a day, and works fine for awhile. No codes of any nature. Local mechanic is ready replace the master cylinder. So before spending the $$$ for that, he would like to make that makes sense to the guru's on this forum.

[DmaxMaverick]

Yep. Unless you can find a leak somewhere (and corresponding fluid loss), it's the MC. Easy job, even if you're a neo-DIY'er.