Slave cylinder travel distance

[Nate]

So the slave cylinder failed spectacularly in my c900 as you guys read in my clutch tool thread. One morning I pushed the clutch in and the brake fluid light came on. I checked under the hood and there was a huge puddle of brake fluid on the skid plate and the reservoir was half empty.

The cylinder is only 5 years old or so. It is not OEM but it's not a scantech either. I remember that I found it at O'Reilly's and it was made in Italy.

I have about 1k miles on a Dave Kennedy 9k clutch setup. He re-machined a c900 flywheel to accept the 9k pattern. The flywheel is significantly thinner than the old one to be able to fit the heavier pressure plate.

Every since the installation, I've had to nearly push the pedal to the floor to shift. It would crunch and be difficult to shift at times. It seemed like I had to "re-learn" the car. Still I shouldn't have to push it clear to the floor. I re-bleed the system, drove it for a while and it seemed better. Until this happened.

The failure seems to be too coincidental to just be random. Is it possible with my new setup for the slave cylinder to extend out too far out and blow the seal like it did? How would I even fix this? I was thinking that I could find some sort of machine bushing to act as a spacer to put between slave cylinder and the bearing to give the cylinder more reach. Or would a worn clutch pedal just exacerbate this issue with my new setup? The car does have 183k on it & the pedal does have a bit of play in it at the top of its travel.

[Jordan]

If the flywheel is thinner then you should shim the the slave cylinder out, or else you will probably blow the slave again.

[Mezzanine]

If the flywheel is thinner then you should shim the the pressure plate out, or else you will probably blow the slave again.

If you shim the PP, then wouldn't you be taking away from clamping force on the clutch disk?

I suppose you could shim the slave out from the transmission housing. Best to machine a bushing, but a few washers could get the job done. What a pain to put in though...

[SwedeSport]

Make a spacer ring to seat behind the throwout bearing. Make it the same thickness as was removed from the flywheel. Maybe that would work...

[DrewP]

My Dave Kennedy 9000 clutch has always engaged a little low too, not as low as yours sounds, but I haven't blown a slave.

5 years on an aftermarket slave is about when I wouldn't question why it blew. As long as the piston in the cylinder doesn't extend so far that the o ring slides off the end of it's sealing surface there's reason extension would make it fail, and it probably would have failed immediately.

[Jordan]

If the flywheel is thinner then you should shim the the pressure plate out, or else you will probably blow the slave again.

If you shim the PP, then wouldn't you be taking away from clamping force on the clutch disk?

I suppose you could shim the slave out from the transmission housing. Best to machine a bushing, but a few washers could get the job done. What a pain to put in though...

I don't know why I said pressure plate. I meant slave cylinder!

[Jordan]

My Dave Kennedy 9000 clutch has always engaged a little low too, not as low as yours sounds, but I haven't blown a slave.

5 years on an aftermarket slave is about when I wouldn't question why it blew. As long as the piston in the cylinder doesn't extend so far that the o ring slides off the end of it's sealing surface there's reason extension would make it fail, and it probably would have failed immediately.

The springs in the pressure plate could wear in as well as the throw out bearing settling into them...just a theory, but it would have to be very close to begin with. Also, certain slaves are thinner than others to start off with.

[99Super]

If the slave is Italian, it could be an LPR. I like them because they are 2-3mm shorter than the factory units so you can get them out of the car w/out having to remove it with the PP/disk. Nice to know about the thinner flywheels potentially creating problems.

[Nate]

Dave said the that flywheel needed to be thinner in order to make room for 9k pressure plate which is supposed to be 3mm thicker. I'm going to the measure the differences between between the stock pressure plate & the 9k one. I should have done this before I put it in...

Things were cramped when I put this in. The c900 clutch spacer tool wasn't thick enough to compress the 9k pressure plate enough to get the whole assembly in. I had to shim the spacer ring with some .070" aluminum to get enough space to get the clutch and slave cylinder in.

[Geoff]

Funny, I just dealt with this. I have a lightened flywheel on my 99 with an earlier 900 turbo clutch. My slave cylinder popped, I picked up an aftermarket one and that one popped too. I started looking at things more closely and found that the flywheel has been machined down too many times. It measures 21.5mm thick and a stock one measures 23mm. I didn't measure the rest of the system since the clutch and slave cylinder are essentially stock (made for that transmission/engine combo).

To solve (I think*) I put a shim behind the slave which sits between the inner cylinder and the transmission housing. It measures 55mm OD x 45mm ID x 2mm thick. http://www.mcmaster.com/#98089a480/=sglxok I used some RTV to hold it to the transmission case to help installation. The recess in the transmission housing is about 5mm deep and the inner cylinder protrudes from the back of the slave about 5mm so this shim effectively spaced the slave out ~2mm while still maintaining the locating feature of the back of the slave in the transmission housing and constraining the inner cylinder from exiting the back of the slave.

I thought about putting a spacer between the slave and the throw out bearing but I couldn't find a tiny one that would fit and it seemed to be a little more sketchy (mostly due to the size). I also thought about just putting washers between the slave body and the transmission housing but quickly scratched that idea when I realized the inner cylinder would pop out of the back of the slave housing because it isn't constrained.

Other things:

I've run a 9000 clutch and flywheel before ('90 or '91 I think) in an '85 but didn't have it machined down any significant amount. Probably just resurfaced. Unless I was using a later C900 flywheel, but I thought I remembered it as being a 9000...

Drilling and fitting a bushing to the pedal is pretty quick and will help solve some of your floppy pedal issues.

*I finished this repair on Sunday and so far I've only driven the car from one driveway to another. But it seems like it will work

[Sam]

Try an F55 slave from a 9-5 or 9-3. They are almost identical to the 900 with a tripod hole setup, and would be worth a try if you have one sitting on the shelf. The F55 got a new slave cylinder in the last years (2008+) which improved clutch feel, making it feel more like modern clutches but with the longer saab pedal.

My Dave Kennedy flywheel in the 9-5 makes the clutch centering tool not work, and makes trans alignment really really hard. I have a kit which i put together from some parts on MC Master to get around the problem, but thats a topic for another thread.

[jdwertz]

Check out this slave from APracing. They are expensive but come with different throw options and have high quality seals.

http://www.apracing.com/product_details ... inder.aspx

[Mezzanine]

Check out this slave from APracing. They are expensive but come with different throw options and have high quality seals.

http://www.apracing.com/product_details ... inder.aspx

Nice find. I couldn't find pricing anywhere- do you know how much?

[gmreider]

Very Nice ! Looking at the info, it seems that the product is really no longer available ??

[Mezzanine]

Very Nice ! Looking at the info, it seems that the product is really no longer available ??

Under the "associated products" tab, it looks like the fitting set is NLA, but not sure about the slaves.