The clutch went out on my Miata last weekend. I manage to drive it 30 miles to home without using the clutch, starting it in gear at a couple red-light. The synchos in the Miata transmission seem to be pretty much go/no go. I had a hard time shifting clutchless compared to other cars, but there was almost no grinding.
The day before the clutch went out totally, the shifting got very difficult, impossible to engage reverse. The fluid level was low in the master-cylinder reservoir. I topped off the reservoir, expecting to see the level start dropping, but figuring I could top it off every few days until I could get around to fixing the problem. After topping off the reservoir, I would have to pump the clutch pedal, after the car was parked, so I probably had some air in the line. The next day, when the clutch completely went out, the m-cylinder was still full, and pumping the pedal didn't do anything.
I'm guessing that it's the slave cylinder. My Miata Enthusiasts shop manual doesn't really give any clues on how to diagnose clutch problems. I'm going to try bleeding the clutch, but wonder if I should look at anything else. If I don't get anything when I try to bleed the slave cylinder, I guess that I can try disconnecting the line from the m-cylinder and seeing if fluid squirts out when I depress the clutch pedal.
Those are the classic symptoms of a leaking slave cylinder. Your clutch itself is probably fine. Replacing or rebuilding the slave cylinder is easy and inexpensive.
About 15 dollars and 15 minutes, plus jack-up and bleed time, is all it takes to do a Mazda (and a whole lot of others!) RWD clutch slave, even for a rank amateur. A slow-moving rookie might be able to turn it into an hour or so job if he wanted to.
Idunno how "wrenchy" you are, so if this is so simplified it comes across as insulting, my apologies. It's not intended to be.
Get a slave rebuild kit from your local parts joint. While you're there, grab some extra brake fluid. A quart or two should be plenty, and leave you enough to top up as needed.
Jack it up and put it on stands, then get underneath. The slave cylinder should be glaringly obvious. If it's not, your vision and/or lighting is too poor. Call an optometrist or electrician before proceeding. :)
Break loose the hydraulic line coming from the MC at the slave - Just crack it. Don't try to completely remove it yet. Trust me on this...
Now undo the two mounting bolts AND THEN, once the slave is dangling by the hose, rotate the slave to remove the line. The whole slave assembly falls off into your hand as a convenient unit. Set it aside for now. (someplace "brake fluid safe")
Using an appropriate container to catch what you're pumping out, pump the clutch pedal until the MC is empty - You've probably got "yuck" in the system from the slave rubber deteriorating, and you want to get rid of it. Don't hesitate to refill the reservoir with clean fluid a couple of times, as pumping some fresh clean fluid through it can only help flush the MC and line nice and clean.
Point the hydraulic fitting of the slave cylinder at your container, and mash the pushrod that's poking out of the rubber boot to get rid of most of the fluid in the cylinder, then pull the boot off of the cylinder and set it and the pushrod that's probably trapped inside it aside.
Use a tiny spritz of compressed air into the hydraulic fitting to pop the old piston/cup/spring assembly out. You just want to pop it out, not shoot it across the county :) Inspect (the bore should be nicely smooth. if it's scored badly, you might need to either hone it, or if it's really chewed up, get a fresh cylinder), rinse out any "yuck" inside with clean brake fluid if needed, "grease" the new cup by dunking the whole spring/cup/piston assembly in clean fluid, and drop it into the cylinder, spring first, then press it into place, being careful not to nick the rubber cup.
Replace the boot/pushrod (Depending on who made it, your rebuild kit may come with a new rod/boot already assembled, or you may have to pull the old boot off of your old rod, and put the new one on it - it may seem like an awful tight fit, but it'll go), then, keeping the hydraulic fitting at the highest point, mash the rod to force out air, and while pouring a trickle of fluid into the hydraulic fitting, slowly release pressure on the rod to pre-fill the slave with fluid, repeating until you don't get much, if any, air out by mashing the rod. (This helps take most of the hassle out of bleeding later) Set the whole assembly aside (keep the hydraulic fitting pointing up!) for the moment.
Attach a clear line to the end of the line from the MC, the same way you would for one-man brake bleeding, and fill the MC. (And keep it filled throughout this operation!) Now bleed it out - GENTLY!!!!! You've got an open system, so it won't take much pedal force to give yourself a blast of brake fluid in the face, or pop the clear line off, forcing you to start all over again. Keep pumping/filling as needed until the clear hose you attached is full of fluid and bubble-free.
Now comes the one tricky part - Removing the clear line, and attaching the hydraulic line to the slave. The idea is to do it as smooth and quick as possible to minimize air getting trapped inside the system. Eyeball your options, and do it as best you can. I like to try to do it from above, but that's just my preference. Turn the slave cylinder, not the hose. Don't worry about getting it cranked down "final-tight" (yet...) Just snug it up as best you can.
Once you've finished, cuss real loud 'cause you forgot to put the little copper washer back on the end of the hose. Pull it apart and put the washer back on. :)
If you went for the "do it from above" method, feed the slave and hose back down to where it lives. Otherwise, just bolt it back into place on the tranny. Crank the hydraulic fitting down solid AFTER you've finished with the mounting bolts.
Do a final bleed. It shouldn't take much more than a few strokes of the pedal, since if you've done it even slightly like right, you've already gotten 90+ percent of the air out in the reassembly process.
Eric, Mine did the same thing today. I got it home by pumping the pedel a lot just before I was going to use the clutch. I had a slave as a spare that I had put a $8.50 rebuild kit in so I made the swap about an hour ago. I have a "speed bleeder" on it so it was a fast job to do. RED is all better now and ready to go. :-) I bleed the system twice a year, but they still go out. It is just one of the things you need to keep up with on a Miata. Take your old slave and clean it up good with "Alki", get a rebuild kit, (NAPA has them) use a little bit of brake fluid on the rubber seal and put it together and seal it up in a good "zip lock" bag so you will have a replacement for next time (and there will be a next time!) NAPA also has the complete replacements too.
Yes, just about anyone can replace the slave cyl. Removing the Right front wheel assy. makes it very easy. Tools: 10mm "tubing" or open-end wrench. 12mm socket wrench (for the hold-down bolts) Note: besure you start all the bolts and tube nut with your fingers so as not to "cross-thread" any of them!!!
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