If you have a fresh slave and freshly-black fluid, your master is toast.
1989 MX-6 GT. ORIGINAL OWNER!! 315K on the original clutch, K&N drop-in, Gillis boost valve, Tokico Blues, OEM RSTB, Energy Suspension poly sway bar bushings, end links, tie rod end boots, AWR poly motor mounts (only the rear one now, and that will be back to a stocker soon - I got tired of the vibration and noise), OEM rear lower tie bar, PGT rear sway bar. Techna-Fit stainless brake lines, AWR trailing links, new OEM lateral links.