Clutch Failure: Master/Slave Cylinder? (Solved, clutch disc failure)
 

So, I have had a clutch failure of some sort. Clutch will not disengage.

It isn't the clutch pedal assembly, I removed that and inspected, and the bracket I installed years ago is still doing it's job just fine. The clutch is 21,000 miles and 1 year (almost to the day) old. Pushing in the clutch pedal DOES move the slave cylinder and pushes on the release lever. However, I REALLY suspect that this is a master or slave cylinder failure, where it's just not pushing far enough.

With the rear wheels in the air, clutch not depressed, I can shift into any gear without much difficulty (and successfully drove it 7 miles home without the clutch rev-matching every shift up and down). If I apply the brake without the clutch pedal depressed, the engine starts to stall. If I apply the brake with the clutch pedal depressed, the engine does not stall, but there is a whirring and light grinding noise. I found some suggestions that the noise might indicate one of the bearing failures, however it could also just be a low speed clutch disc not fully getting disengaged. I would expect with a bearing failure that I wouldn't be able to shift as predictably and easily as I did.

I don't think it's a release fork that slipped off the release bearing, since I can't make it budge by hand AT ALL. Not even a tiny bit. I have to use the clutch hydraulics to do so. I would expect that if it had slipped off at all, I'd probably have at least some little bit of play to it.

So my gut tells me it's one of the cylinders that just isn't pushing far enough on the release fork.

I will have to order parts in the morning, and it's tempting to just order both, but I really want to be sure I got the problem, and I don't have much time to correct it before my track event next weekend.

Any ideas on how I can test the master cylinder? How to test the slave cylinder? Independent tests are preferred, so I can find the culprit. If I had another 8 on hand, I'd measure the movement of the release fork to see how far it should be moving and measure the movement of mine for differences. Maybe someone else that has their 8 up in the air could check :suspect:

:D:

Any other ideas?

Not finding anything relevant on the site or in Mazda's OEM documentation.

Do you have any adjustment left at the pedal? It may have just drifted out of adjustment.

Yeah, I do have plenty of adjustment. It's actually never been adjusted from original 7 years and 110k ago :)

This wasn't a slow failure though, one shift to the next the pedal suddenly just stayed on the floor and couldn't shift into gear until I rev matched, had to pull the pedal up with my toe. Never stayed on the floor after that, but still never disengaged the clutch.

Something broke in that shift.

Hmm. I'm sure you tried pumping it. I remember a similar failure of the master cylinder on my miata, but that was years ago. If the pedal stayed down then I'd guess it's the master cylinder, but that's just a guess.

Bleed your slave, if ur fluid comes out like in my picture. your master has failed.

otherwise, it's your slave.

been there and done that years ago :( SEARCH for my thread u noob ! :lol:

https://www.rx8club.com/attachment.p...1&d=1351473723

:lol:


Actually, I was looking for your thread! The only references to failure I could find that weren't related to clutch pedal assembly failure was your comments. But you post a hell of a lot, and just try searching for clutch slave/master terms and see if you can sift through all of your own posts of: "it's your pedal assembly, search noob!" :lol:


Thanks :)

If your pedal is sticking on the floor then you have completely lost pressure. Do you have a leak? Is there still lots of fluid in the reservoir?
You could check if the master is pushing fluid by disconnecting the clutch line at the bottom and holding your finger over the end and have you misses press the pedal. Obviously you will have no idea of pressure but you will be able feel if the fluid coming through the clutch line. (you might want to wear goggles) I ordered a new Master cylinder for $35 so they are not very expensive.

It's not "sticking" to the floor, as in plural. It just did once.

No fluid loss at all, not even wetness. Fluid line still just below the high line (brake pads fairly new) It's certainly providing pressure, since the slave is moving the release fork, just apparently not enough for sufficient disengagement.

Rock Auto has a Master for $26, Slave for $45, but next-day shipping is $127 :shock: Looking around to see what might be closer. I'll do that if I have to, but I struggle to justify tripling the cost just due to shipping. 2-day to get here Wednesday is a bit too close to call for my track even this weekend, since I am gone all day thursday, and leave friday morning for WV.

Also seeing "rebuild kits", but have no idea if they are actually viable or not.

Rebuild kit should be all you need. I still am betting on the master cylinder.

Reading on rebuilds of them, lots of comments regarding honing. I think I'll just get brand new ones to be safe.

Well, ordered. Will pull them tomorrow, and pray that my next day shipping will still actually be getting here Tuesday, and not be hurricane delayed.

At least I was going to be replacing all the brake fluid anyway :)

sounds like a master/slave problem due to the pedal flooring, regardless you never change only one lol Always do them both because they wear together and if you make one stronger it puts more stress on the other one and it will soon fail. You're also supposed to change them out when you change a clutch but most people don't know this either. Good luck though :-)

I would bet slave at this point...usually when the master fails it will leak into the pedal area...when the slave goes it leaks into the rubber bellows on the end of the pushrod...and sometimes is hard to see

Make sure that the bleed screw is tight...have seen them loosen and even brake off...speedbleeders are the worst for that..they have thin walls from the ball valve and aren't as strong as standard plugs

The system is really simple...the master plunger gets pushed in by the clutch pedal...that pushes the plunger out on the slave...so replacing both and no leaks and it should be good :)

Nope, not mine, not a single bit of fluid leak out, it just failed internally.

when I bled the line, there were so much metal particles out of the fluid I was like wtf? That's why I didn't even bother and bought a new Clutch master and be done with it. I still have the failed part, no time to dissemble it to see wtf is going on inside.

The bad fluid never made it backwards up to the Brake Master, you can tell cuz when you disconnect the line from brake master to clutch master, everything is clear. it's anything after the brake master that's loaded with crap.

parts replaced, bled for maybe 2 quarts, all the crap came out, everything back to normal :)

Got the new slave and master last night at 5pm (which was overnight shipping from Monday). Installed them last night, bled clutch line, each of the 4 brake corners, and the clutch line again. Best I can get is a partial disengagement that starts burning the clutch at idle. Bled again this morning and no change.

I'll limp it to a shop and have someone else pull the transmission. Have to miss my first track weekend.

So frustrated right now.

Try pulling the starter, then feel around for clutch chunks in the bellhousing.

Well, I basically haven't done anything toward this since the last post, and was going to start pulling the transmission today (I can't bring myself to pay someone for labor for something I can do), and pulled the starter as Marc noted. Wadded clutch material on the starter nose, stuck to the flywheel teeth, visible elsewhere. So unsure as to the cause of the failure still, but clearly clutch disc failure. Exedy Stage 1, not really sure why this one lasted only 21k when my OEM factory one lasted 90k. :dunno: The clutch disc and pressure plate would have been moved to the reman when I had the engine replacement, wondering if the techs messed up something there.

This was another clutch disc failure. One half of the disc itself separated from the center metal plating, completely separated. Unknown if the rip through the clutch material was pre or post separation.

https://lh6.googleusercontent.com/-a...2012-11-17.jpg
https://lh3.googleusercontent.com/-m...2012-11-17.jpg
https://lh4.googleusercontent.com/-e...2012-11-17.jpg
https://lh3.googleusercontent.com/-T...2012-11-17.jpg
https://lh6.googleusercontent.com/-s...2012-11-17.jpg
https://lh4.googleusercontent.com/-s...2012-11-17.jpg
https://lh5.googleusercontent.com/-c...2012-11-17.jpg
https://lh3.googleusercontent.com/-Q...2012-11-17.jpg

nice! mine was starting to do that, thank god it slipped before it did that. everything was furry when i pulled it apart like yours though

Are you going back to OEM or getting another after market

I don't really think this was just a worn out clutch, since my OEM one lasted 4yrs 90k, and this one only lasted 1yr 21k. I'm easy on my clutches, if anything the OEM one took more abuse since I would clutch-drop off the line every run in autocross (best launch I found for the surface and tires I had to work with), but never autocrossed on this clutch (too many other things kept me away this past year)

Haven't decided. OEM is more expensive, grabs a bit less, but also has less chatter that I never really liked in this one. This was Exedy Stage 1, so it is pretty close to OEM even so.

lmao! so did mine, you'd think in 3 engines someone would have bought a new disc....

i didn't measure it, but the old disc was like half the thickness of the new one

Could it be an issue of exceeding facing burst speed threshold?
If so, seems like a lemon clutch disc.

I'd expect Exedy Stage 1's to have facing burst speed thresholds that will accommodate RX-8 high RPMs.

The following info might be helpful: Causes of Clutch Disc Failure - Auto Clutch Ltd

Hmm:
That does sound and look exactly like what happened...

...and looks like the failure is pointing at my installation a year ago? Or is the "faulty adjustment procedure" only applying to the slipping?


It's looking like I did something wrong last year I think.


Re-re-re-edit:
I didn't remove/replace/resurface the flywheel last year, though it was only on for about 4,000 miles before my reman installation would have swapped it to a new flywheel.