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Old 08-11-2008, 01:02 PM   #1
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Default Clutch slave cylinder failure

So my clutch slave just failed yesterday. It was a rebuilt unit that has been on there for about 15K miles. I was driving home and the clutch stopped working. The master cylinder is out of fluid, no leaks anywhere down to the slave cylinder, fluid leakage evidence on the boot.

So I am probably going to get a kit and rebuild it. It is $8 at the local Auto Zone (in stock). Before I do, does anyone have any ideas on a mode durable solution? I have read up on it here and at m.net but all I see are rebuild versus replace arguments, no other alternatives. A failure at 15K is lame, especially when it is on the cold side of the engine and I replaced the master cylinder, the flex line (braided stainless from FM) and flushed it all thoroughly with new fluid when I replaced the slave.
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Old 08-11-2008, 01:44 PM   #2
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The slave is cast, and the surface is rather porus. I suppose you could sleeve it, but that's a lot of work. From my investigations, the new ones are no better.

I bought a used one and two rebuild kits. I rebuilt both, and keep the second as a quick-change spare. Honing lightly seems to help, but I have no long term data to back it up.
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Old 08-11-2008, 02:49 PM   #3
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I have rebuilt the slave or slave/master on every miata that I've had on the road. I just keep a spare kit at home. Seems to just be nature of the beast, but 15K seems pretty weak. Might have been an imperfect bore. I generally do a little flap lap with some emery.
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Old 08-11-2008, 03:15 PM   #4
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Quote:
Originally Posted by rleete View Post
The slave is cast, and the surface is rather porus. I suppose you could sleeve it, but that's a lot of work. From my investigations, the new ones are no better.

I bought a used one and two rebuild kits. I rebuilt both, and keep the second as a quick-change spare. Honing lightly seems to help, but I have no long term data to back it up.
Sleeving is an interesting idea... I was thinking about coatings/platings but a thin wall SS sleeve with an interference (press) fit could be easier. The slave would need to be bored out for the sleeve of course.
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Old 08-11-2008, 11:00 PM   #5
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Taiwan quality control seems to suck w/ these rebuild kits from Vatozone. Bought a rebuild kit for the slave. First plunger was super tight and tore. Returned it. Second plunger was super loose. Ended up buying a new one instead. Took three times for a fix. Not worth it to me.
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Old 08-11-2008, 11:14 PM   #6
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is an na/nb slave the same, how bout rx7?
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Old 08-12-2008, 12:09 AM   #7
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Well this evening I installed the rebuild kit and bled the system. It is working well, better than it has been working recently even before the failure. We'll see if it holds up.

I did notice that the inside of the cylinder felt a little rough though it was clean and had no rust spots. I was planning on honing it, that is until I realized the hone I bought at Autostoned was too large, damn it

Good question about the RX7 unit. It would be important for the slave bores to be about the same size so that the clutch action would be similar.
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Old 08-12-2008, 12:29 AM   #8
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I have been wondering the same thing I have been thru 2 slaves on my miata and 2 on my integra as well as broke my shift fork in half on my integra. I just got done pulling the transmission to replace the fork on my teg. Anyways just hoping there may be a solution.
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Old 08-12-2008, 12:45 AM   #9
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I rebuilt my master, just waiting for it to fail again
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Old 08-12-2008, 09:15 AM   #10
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I'm too lazy to look up the slave cylinders, but I highly doubt that the castings are shared applications. However the rebuild kits do cross applications to all sorts of other cars.
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Old 08-12-2008, 10:03 AM   #11
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Anyone know what the bore size is? I think maybe a reamer, say .001 oversize to true up the bore might lead to longer life. It would not only make it round, but should improve the surface enough for a better seal.

They aren't that expensive. Sombody measure a slave, and let me know the size.
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