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-   -   Clutch Slave Cylinder Measurements (https://www.rx8club.com/series-i-tech-garage-22/clutch-slave-cylinder-measurements-242862/)

RIWWP 02-12-2013 04:08 PM

I didn't do it yet, so I don't yet have the justification for kicking myself over this particular issue yet. It would be presumptuous and inefficient to start kicking now.

I do expect that your advice is in the correct direction and will solve the issue.

RIWWP 02-12-2013 09:38 PM

Well, no solid change. Slight improvement in that the release bearing is only faintly contacting the pressure plate forks, so the noise dropped away some, but not completely. I even bled the CSC by providing pressure on the CSC by hand from the clutch fork side, and I could apply enough pressure (with the bleed screw closed) to push the CSC piston almost completely back into the bore. It would still return back to a 'resting' state applying slight pressure to the clutch fork.

And somewhere in there the clutch interlock switch won't depress far enough with the clutch motion to allow the engine to start. I can manually push in the plunger and it will fire right up. Maybe another 1/8th of an inch of interlock switch plunger motion in order to close the needed circuit.



On top of all of that, I discovered that the access plate cover that sits on the rear iron behind the oil filter is missing, so there is a big hole in the top of the rear iron where stuff can fall in if luck swings that way. The dealer had to have removed it or forgotten to install it when they were doing the reman replacement.

McKennaR 02-12-2013 10:43 PM


Originally Posted by RIWWP (Post 4425891)
Well, no solid change. Slight improvement in that the release bearing is only faintly contacting the pressure plate forks, so the noise dropped away some, but not completely. I even bled the CSC by providing pressure on the CSC by hand from the clutch fork side, and I could apply enough pressure (with the bleed screw closed) to push the CSC piston almost completely back into the bore. It would still return back to a 'resting' state applying slight pressure to the clutch fork.

And somewhere in there the clutch interlock switch won't depress far enough with the clutch motion to allow the engine to start. I can manually push in the plunger and it will fire right up. Maybe another 1/8th of an inch of interlock switch plunger motion in order to close the needed circuit.

On top of all of that, I discovered that the access plate cover that sits on the rear iron behind the oil filter is missing, so there is a big hole in the top of the rear iron where stuff can fall in if luck swings that way. The dealer had to have removed it or forgotten to install it when they were doing the reman replacement.

If you can push the CSC rod back into the body with finger pressure with the bleeder screw closed, yet there isn't enough "push back" in clutch itself to prevent this light pressure applied by the CSC at "rest" from partially releasing the clutch... something's up.

Re: the interlock switch, whenever mine acts stupid I remove it, pull on the plunger to extend it fully, reinstall it, stomp the clutch once and it works for a few weeks. I know that's the wrong answer, but I can't be bothered to buy a replacement now.

It's a common FoMoCo / Motorcraft switch, available at O'Reilly's but I don't remember what the price or P/N is. I'd say between $20 - $25. Tasca Parts is down tonight, but Jim Ellis has it for $37. The Mazda P/N is D374-66-4D0A.

TeamRX8 02-13-2013 06:22 PM

Did you go back and check the pedal position/master cylinder rod clearance after the bleed? You will need to make sure it's clear again

RIWWP 02-19-2013 07:33 AM

I pulled the transmission Sunday afternoon. The Exedy Stage 1 clutch disc was already starting to fray and stuffing the pressure plate with clutch material. Less than 100 miles on this clutch.

The last one failed in only 20,000 miles, I'm not sure why I went with that one again. Short story is that I'm not willing to put that clutch back in. Ordered an OEM clutch and will have it today.

Ray expressed concern about inconsistent or inaccurate dimensions for the Exedy, including mentioning that he is having trouble with them elsewhere as well.

Yeah, it doesn't make a ton of sense that the manufacturer of the OEM clutch would have trouble making an aftermarket variant. But going back to OEM either way.

viprez586 02-19-2013 08:28 AM

Interesting. I opted out of the Exedy after hearing it was the same manufacturer of the OEM disc.
Went with an ACT HD clutch, of which I was somewhat skeptical of. (along with the ACT pro-lite + counter weight). After doing my clutch adjustments the clutch is awesome. It squeaks every now and then when it's cold, but the pedal feel is great with better engagement then OE (IMO).

Interesting you found an issue though, snap some pics!

RIWWP 02-19-2013 11:30 AM

After all our discussions, I wouldn't be surprised at all.

Thanks again for putting up with me through all of this Ray.

TeamRX8 02-20-2013 12:43 AM

No brand affiliation, just have always used OE or OE replacement by Exedy without issue on my RX8

I've put so much abuse on the OE clutches it amazes me why anyone with an NA Renesis feels like they need to upgrade it. The one I just took out has at least several hundred high rpm drag launches on it and still has a lot of life left in it. It's probably at least my fourth or fifth one, haven't really kept count. My own advice is that unless you have added significant power mods then stick with either OE or OE replacement.

nycgps 02-20-2013 04:00 AM

what did u do to ur clutch? seriously! ;)

that sucks, well mine has been holding up well and autox it couple of times. shit luck i guess?

RIWWP 02-20-2013 10:28 AM

OE clutch is in, everything installed last night, bled the clutch system just now. Lighter pedal pressure than the stage 1, but quick tests with the car in the garage seem to indicate that everything is back to normal with my clutch system.

Will be a few hours before I can take a break from work to give it a thorough test drive. Noises and weird pedal behavior are gone.

NMRX8dad 11-22-2018 07:49 AM

We have a similar problem but in the opposite direction. When my son and I installed a new clutch in his 2004 rx8 with a six speed transmission, we had to adjust out the clutch fork pivot bolt inside the bell housing 1/4" because there was too much distance between the slave cylinder push rod and the clutch fork. We thought maybe the clutch fork was bent, but we had two mechanics look at it and we ruled that out. We thought maybe we got the wrong clutch kit, but we ended up ruling that out. Are adjustments like this common?

horrorsbob 11-12-2021 09:26 AM


Originally Posted by McKennaR (Post 4424879)
Let me know if you need some more, these are hardly scientific.

The cylinder is completely dry so its natural rest point might be a bit off.

I can get the one on my car tomorrow if needed.

Looks like the rod from tip to where it seats in the fork is a touch over 1". The rest of the graduations should be visible on the tape measure. Pic 1 is at rest, 2 is compressed and 3 is fully extended to the limit of the boot.

I know it's a long time ago but have you still got the photos of the clutch slave. They will not display full size on the forum. The dimensions will be very helpful before I source a slave cylinder for me RX8 gearbox attached to an AJ30 3.0.


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