Problems with Clutch

My clutch pedal all of a sudden lost pressure and couldn't be shifted. I was told this was a hydraulic issue and to check the reservoir and slave cylinder. I have hydraulic fluid in the reservoir but it is really dark. The slave cylinder appears to be normal and dry. I applied pressure to the boot on the slave and no fluid was visible. I had my son press the clutch in and the piston only moves the clutch fingers about 1/4 to 1/2 inch. I opened the bleed valve and had my son press the clutch. Fluid was eject with pressure. I tightened the bleed valve back and then had him release the clutch. Do this indicate a bad slave valve? I was told when the slave valve goes, it is usually leaking somewhere. Any advise or help would be most welcome.

What kinda car?

You should be able to see the backside of the master cylinder from under the dash. If it has fluid drooling out the back, then you need the master cylinder.

Good idea to replace the slave at the same time, as they usually fail in pairs.

I have a 1996 Mazda Miata with six speed manual trans. I don't have any visable leakage.

Probably master, replace both, they're cheap.

Given that the master cylinders in RX-7s last about two years and that the Miata is 80% RX-7 I'd say it needs a master.

Even before you figure that the slave is not leaking and the hydraulics aren't doing anything (which ALSO says master).

What probably happened is the bore rusted/corroded in the master and it is bypassing. Very very common. That'll teach you to not flush the hydraulics every year.

Well I went to the parts store (Auto Zone) and bought both the Master and Slave Cylinders (they were $20 each). I decided to put the Master Cylinder in first, mainly because there were no leaks at the Slave Cylinder. Upon putting the new Master Cylinder in and filling and bleeding the line, the clutch is working normally now. I will keep the Slave Cylinder for now and see if it acts up in the short term.

Best to change both at once, cuts down on cross contamination and such.