The clutch in my '96 Miata went from being fine in the morning to
useless at lunchtime. The clutch pedal feels like there is no pressure
at all. The reservoir is full, but the fluid looks dark at the bottom.

I replaced the slave cylinder and went to bleed it, but noticed that
when the clutch is depressed the bracket that presses on the slave
cylinder piston does not move. Would this mean the master cylinder is
bad?

Thanks,
Jim