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Clutch Slave Cylinder Measurements

Old 02-09-2013, 06:35 PM
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Clutch Slave Cylinder Measurements

If anyone has an original or dealer obtained clutch slave cylinder laying around not installed (or wants to pull theirs), I'm looking for some measurements and pics of it.

Primarily the the length from where the rod actually seats into the clutch fork to the bleed screw, though some other dimensions may be useful. I am becoming increasingly confident that my "OEM replacement" slave cylinder has a variance on that length, being slightly longer than OEM, a tenth of an inch or less, but still longer. Yes, it matters for correct clutch pedal adjustment.
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Old 02-10-2013, 08:52 PM
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yes the pedal needs the full sweep, so if something is off, its off!

if all goes well i should have one apart later this week, if nobody else has answered in a day of two, please shoot me a PM, i'd be happy to measure
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Old 02-11-2013, 12:02 AM
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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.
Attached Thumbnails Clutch Slave Cylinder Measurements-2013-02-10_23-09-32_241.jpg   Clutch Slave Cylinder Measurements-2013-02-10_23-10-22_667.jpg   Clutch Slave Cylinder Measurements-2013-02-10_23-10-48_568.jpg  

Last edited by McKennaR; 02-11-2013 at 12:30 AM.
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Old 02-11-2013, 05:58 AM
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Perfect, thanks!

I should be able to compare that to mine well.
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Old 02-11-2013, 07:33 AM
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Are you having an issue getting it to align on the bellhousing?

.

Last edited by TeamRX8; 02-11-2013 at 07:44 AM.
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Old 02-11-2013, 07:42 AM
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No, the release bearing is in contact with the pressure plate with the hydraulic system at full relax, including if I completely pull the pedal assembly plunger back out of the master cylinder. I believe the pressure plate is loaded from it too, even if slightly, from what I can feel through the clutch pedal. I haven't had this on the factory clutch or on my last clutch. When the last clutch burst, I replaced the slave cylinder, master, clutch disc, pressure plate, and release bearing. I didn't mess with the pilot bearing since that is new as of the reman 14,000 miles ago.

Unbolting the slave cylinder from the bellhousing is a noticeable release of tension on the clutch fork. I don't recall that from the last clutch, or removing the original slave cylinder. I didn't notice it on installing either, but then there was plenty of air in the system from the replacements.

Last edited by RIWWP; 02-11-2013 at 08:00 AM.
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Old 02-11-2013, 08:25 AM
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Did you try bleeding it? This would release the pressure if the slave piston is not fully bottomed out in the bore ( push-type slave). The system is designed to be self -adjusting as the clutch wears. Installing a new clutch changes the engagement point from where the worn clutch was.

Edit: not really clear to me what you're doing overall. You just replaced all those parts and now have this issue? If so that means it was likely already bled.


.

Last edited by TeamRX8; 02-11-2013 at 08:32 AM.
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Old 02-11-2013, 08:45 AM
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wow that's odd. On DSMs we'd have to shim the clutch fork to make the clearance correct.
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Old 02-11-2013, 08:56 AM
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Sequence of events:
- Clutch pedal went to the floor on a shift and had to manually pull it up, clutch remained engaged clutch pedal would not disengage it. I limped it home.
- Inspected clutch pedal, no damage, worked correctly
- Bled the slave 3 times, no change
- Replaced master and slave (with many associated bleedings), no change
- Pulled the transmission, found the clutch disc had burst
- Replaced the clutch disc, pressure place, and release bearing
- reinstalled the transmission
- rebleed the slave as well as brake master cylinder.
- Have a devil of a time trying to get the clutch pedal adjusted properly. At first, engagement was right on the floor, though I could adjust that up. The bigger problem was that you can feel that it not fully disengaged with the clutch completely relaxed, as well as an audible scraping noise from the bellhousing. Noise continues unchanged with the pedal plunger backed completely out of the master cylinder. Yes, I greased the bearing.

Unfortunately I threw out the original slave cylinder weeks ago, but I remember thinking that the ball part of the slave that sits against the clutch fork looked slightly different than the original slave. Cylinder housing, bleed screw, boot, internals were all the same, just a slightly different shape to the thickening that the clutch fork rotates on.

I unmounted the slave yesterday and found that there was a definite relaxing of the clutch fork, and the slave was now out of alignment of it's bolt holes. It takes a fair amount of force to get the slave into position now as I am clearly have to lever against the pressure plate. Without the slave mounted in position, I can freely move the clutch fork around, and I can feel where it contacts the pressure plate. So I know that there is a possible position for it to be in where it isn't contacting it and this isn't an internal issue.

I'm thinking that I do actually have a difference in the slave cylinders between this one and the original, and this "oem replacement" actually isn't. With the problem point being that it is increasing the length from the mounting point to the minimum clutch fork relax point, adding load to the clutch fork forcing a partial loading to the release bearing on the pressure plate.

I'm ready to order a new slave from Mazmart to be sure to get an OEM one, though I figured before I do that I could measure out the lengths to see if I have a variance to an OEM one. If I don't, then this theory would be sunk and I'd have to keep searching for an answer.

Obviously I'm trying to avoid pulling the transmission again.
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Old 02-11-2013, 09:01 AM
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I'm thinking through how air in the line would affect it. I was assuming that it would be like the brake system, where air in the line means that you can't obtain full extension at the other end of the line, because the air is getting compressed rather than the fluid moving, to a degree in proportion to the amount of air the line.

If this is followed with the clutch line, then I'd have problems getting full extension with the clutch, not problems with full retraction?
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Old 02-11-2013, 10:03 AM
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Not trying to point you in the wrong direction, but what happens when the slave cyl is in place on the bellhousing with the clutch fork pressing back at it and without pressing on the pedal, you open the bleed screw?

I know you stated that you've messed with the rod on the backside of the pedal, but did you do it before or after bleeding? Is there any play at the top of the pedal stroke? According to the FSM there should be about a pedal-pad-thickness worth of play when the pedal is fully released.
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Old 02-11-2013, 10:13 AM
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The problem isn't at the pedal, since I can completely remove the interaction between the pedal and the clutch master cylinder and I still have engagement of the release bearing. What I do with the pedal is going to have to come after getting the rest of the hydraulics correct.

Your suggestion about opening the bleed screw with the clutch fork tension on it is an interesting one. In theory the clutch fork pressure should squeeze out some of the fluid. I'm not aware of any valving on the master cylinder that would hold too much fluid in the line, but the pressure still does exist there. That's certainly a good thing to try, to see what happens. It's free and just might solve my problem?
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Old 02-11-2013, 10:29 AM
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You can go buy a piece of aluminum or steel round stock at your local hardware store and make a shorter push rod too. That is if the rod is easily removed. (Another trick I did with the DSM to get correct clearance w/o pulling the trans to shim the fork.)

Easily done with a bench grinder.
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Old 02-11-2013, 10:50 AM
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Originally Posted by RIWWP View Post
Your suggestion about opening the bleed screw with the clutch fork tension on it is an interesting one. In theory the clutch fork pressure should squeeze out some of the fluid. I'm not aware of any valving on the master cylinder that would hold too much fluid in the line, but the pressure still does exist there. That's certainly a good thing to try, to see what happens. It's free and just might solve my problem?
that's what I suggested earlier as well in post#7, but I wasn't sure if you had already bled it since the parts install, the system is self correcting for wear so the takeup position changes between a new vs used clutch
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Old 02-11-2013, 12:17 PM
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Originally Posted by TeamRX8 View Post
that's what I suggested earlier as well in post#7, but I wasn't sure if you had already bled it since the parts install, the system is self correcting for wear so the takeup position changes between a new vs used clutch
Yep!
Back when I had my warranty engine done, I had the tech replace my clutch under the table. He never adjusted my clutch and it grabbed right by the floor when I got it back. I figured "Hey he's good at his job" but during the break in period I got massive amounts of chatter and from time-to-time an unpredictable engagement from a ACT street clutch and thought it was very odd. Did some free-revs in 6th gear one time after coming home from work and found the clutch dragging when disengaged.(Creeping forward when revving).
Climbed underneath and adjusted the master out to increase the plunger distance and the clutch felt literally 10x better. Rarely ever do I get chatter, engagement is perfect and very predictable. I highly recommend it after any clutch, master cylinder, slave cylinder replacement. (Well duh, but a ton of people forget after clutch replacement)
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Old 02-11-2013, 01:47 PM
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Originally Posted by TeamRX8 View Post
that's what I suggested earlier as well in post#7, but I wasn't sure if you had already bled it since the parts install, the system is self correcting for wear so the takeup position changes between a new vs used clutch
At your prior post I was thinking of bleeding: "having my wife apply clutch pressure to the system as I bleed out the air". I wasn't considering a bleed method that let the system depressurize itself. Now that I have corrected that misperception, I agree that I need to do it that way too.
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Old 02-11-2013, 04:24 PM
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1. When your slave cyl is on the car, if it's 100% bottomed out in it's housing and still exerting significant pressure on the clutch fork, something's wrong with the slave cylinder.

If the above isn't the case, try this:

2. Disengage the pedal rod from the CMC entirely, then crack the bleed screw on the CSC. This should force some fluid from the bleed screw with the pressure of the clutch fork (again, providing #1 isn't true).

3. Close the bleed screw, go back into the car and adjust the rod that goes into the CMC according to the FSM. You should have bout 1" of play.

If the problem returns then something's F'd in your clutch hydraulic system. Perhaps its the CMC if your CSC measures out correctly and properly retracts back into the body with the opening of the bleed screw, assuming pressure from the clutch fork.
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Old 02-11-2013, 06:14 PM
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Yes, that has entirely been the problem. I never considered the possibility of too much fluid in the line, because I was (and still am technically) unaware of a valve in the CMC that would prevent the fluid from returning to a proper balanced volume, like the brake system.

Apparently there is such a method in place, otherwise the pressure from the clutch fork at full relax would have forced the fluid back up into the fluid reservoir. Or something is jacked up with either the CMC or the CSC that is preventing this return flow of fluid.

It can't be a complete prevention, since the clutch hydraulics can still fully disengage the clutch disc, and releasing the pedal does return stuff back in the opposite direction, and it does so consistently and to a specific point.

I am still at work (long office days on the days I go into the office), and will be testing this theory out tomorrow morning.
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Old 02-12-2013, 04:20 PM
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kicking yourself in the butt yet?
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Old 02-12-2013, 04:23 PM
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Not yet

I've been slogging through this work stuff all day so far. Will be another hour or so before I can take a long enough break to do what I need to in order to justify and then start the self applied kicking.
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Old 02-12-2013, 04:32 PM
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It was an off-handed way of asking if you opened the bleed screw yet.
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Old 02-12-2013, 04:33 PM
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Yup, understood.
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Old 02-12-2013, 04:47 PM
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So you didn't do it yet?
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Old 02-12-2013, 04:48 PM
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Originally Posted by TeamRX8 View Post
So you didn't do it yet?
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Originally Posted by RIWWP View Post
Not yet

I've been slogging through this work stuff all day so far. Will be another hour or so before I can take a long enough break to do what I need to in order to justify and then start the self applied kicking.
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Old 02-12-2013, 05:06 PM
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wasn't clear if you didn't do it or you didn't kick yourself in the butt yet, lol
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