Miata hydraulic help please

I was at Mid Ohio this weekend with my '91 spec miata. The car ran great yesterday, but this morning after about 45 min on track (in the wet) it became hard to shift. I came in, let it cool off, and went back out. This time, it only took a few laps before it became really difficult to shift. I came, having to pump the clutch to get it to work at all. The clutch fluid was dark black, but at its normal level. I would have thought that if the slave was bad it would have puked the fluid out, and likewise for the master.

So if I'm not losing fluid, what could it be?

Swap the slave and master cylinders. Easy and cheap to do. If you're still having the problem, then dig deeper. There was another thread about this recently.and it turned out to be a faulty clutch disc.

I am likely the "other thread" that you are referring to with the spring that popped out of the clutch disk:

https://grassrootsmotorsports.com/forum/grm/miata-suddenly-very-hard-to-get-into-gear/117072/page1/

Bad master bad slave due to lack of maintenance.

Brake fluid is not black.

bentwrench wrote: Bad master bad slave due to lack of maintenance. Brake fluid is not black.

Brake fluid has turned black in the clutch system of every Miata I've owned. It goes from fresh fluid in the whole system to black fluid in about a week

The master cylinder is the easiest to replace.

One way to check the slave cylinder is you can turn the wheel left and reach through the wheel well and push back the dust boot. If its filled with oil, you need a new slave.

That's the first thing to do - check for fluid in the boot. Since you can pump it up, that does sound like a hydraulic problem.

Black clutch fluid is normal. My theory is that it happens because there's so much more movement of the fluid than with the braking system, but it definitely turns dark very quickly.