Clutch or shifting problem/Not really sure

In theory this could be either the clutch master or slave cylinders. In practice with Miatas it is almost always the slave cylinder. Check your fluid level. It is probably low, although sometimes the slave will allow air in without visible leakage.

Get a new slave cylinder and swap it out. It's held on by one 14mm bolt. You will also need a 10mm flare nut wrench for the pipe. A regular wrench will almost surely round off the nut. Fill the new cylinder with brake fluid before you bolt it up. Bleed the system and you should be good to go.

this may also be a helpful resource... clutch slave cylinder

I think that you are missing a bolt down there. :-) The slave cylinder should have two bolts holding it in place, and these are 12mm, iirc, not 14mm.

All it really takes is thinking about using a regular wrench for long enough to round off the bolt heads on the hydraulic lines. ;-)

Ok, you got me here. Why would you need to fill the new slave cylinder with fluid before bolting it back on?

Pat

You're right. They say the memory is the first thing to go. I can't remember the second thing... ;>)

It makes bleeding easier if the slave cylinder isn't one big air bubble.

What were we talking about? ;-)

Gotcha, I will do that next time. I haven't replaced anybody's miata slave cylinder in at least a week, so one should be coming up soon....

Pat

Eases/shortens the process of bleeding the system. (Experience talking)

Ok, I told Natman that I would try it next time, but.......I have done either 5 or 6 M1 miata slave cylinder replacements in the last 6 years, along with 2 clutch master cylinder replacements, so I am fairly familiar with the system as well.

How much air are we talking about displacing? I know that it is not much, there is a small reservoir, small slave cylinder, and a very short hydraulic line. My last slave cylinder replacement had a speedbleeder so it was a quick process to hook up a tube and drop the end in a glass of brake fluid. I think that I refilled the small master cylinder twice before there were no more air bubbles, it used very little of the large can of brake fluid that I had. The entire bleed process took about 5 minutes on a completely empty system once the tools were gathered, how much time are we saving here? It has also been a very quick process when I have used a conventional bleed valve and a pedal-pushing helper. Even gravity bleeding takes very little time on the slave cylinder.

With a speed-bleeder, the only extra work is a few extra pumps on the clutch pedal, which seems like it would be easier than bolting a part on in an inconvenient location while trying to keep it full of fluid. Even without a speedbleeder, we are talking about 3 or 4 extra turns on the bleed valve, not a lengthy or difficult process.

Pat

Dunno about you or anybody else, but when working on my 626 (which uses the same clutch system as your Miata - Only difference I know about is that the "pin" between the slave piston and the throwout lever is about half an inch longer than yours) I find it much easier to fill the slave cylinder, pump the pedal until the line (which is disconnected) is full, screw the line to the slave, and then place and bolt the slave. "Keeping it full" past the "screw the line to the slave" step is a non-issue, since at that point, you've got a closed system.

I find that there seems to be a fairly major issue with getting the fluid from the master "over the hump" and down the line far enough to fill the slave if I start with the slave "dry". By pre-filling the slave (and pumping up the master until the line is as full as I can get it - maybe losing a few drops while threading the slave onto the end of the line) then placing and bolting, I find that it rarely takes more than a couple (as in 2 or 3) strokes of the pedal to achieve a good bleed, since there's practically no air anywhere in the system when I start.

(Then again, I may be using a slightly "lower standard" for "good bleed" on the clutch than I would for brakes - A little mushiness in the clutch is nowhere near the concern that mushy brakes are)

Not pre-filling means (at least it has for me, so far) an extended period of pedal-mashing before I see anything even slightly like pressure appearing at the slave.

Gravity-bleeding the clutch has proven all but impossible in my attempts

- It's that "the line loops up higher than the MC, then drops down to the slave" problem again - You can't gravity-bleed without a "live" siphon in place, and until you get the fluid "over the hump", you don't get a siphon - That's some catch, that catch-22! :)

So for me, the obvious choice is to fill the slave before installing it.

Ok then, damn you, I will fill it up next time. ;-)

Thanks for the easy to understand explanation. (seriously)

Pat

De nada... It's what Mazda people do :)