Back at it again on my off/on battle to have the pedal feel like everything else with a hyd clutch around here (ie. newer car). Just want to run this past some folks to see if you either think I've finally "got" it or I'm destined to get pissed off again, and if I do have it finally, maybe this will help some others out since what I did was never suggested.

To start, I have the older CNC master cylinder and single line hyd bearing w/o the bleed in the line from the master to slave. I have a 3.71" bellhousing face to pressure plate measurement which Keisler said "should be OK" even though its over the 3.625" max that's always quoted.

Symptoms were a "dead" pedal for 2" of travel. I had previously force fed the bearing and line from the master to have the slave piston extended out to the pressure plate and also bled out the master prior to connecting the 2 up. Right out of the gate, this gave me a good pedal right from the top... which after slow pedal strokes (for the heck of it) ALWAYS degraded into a 2" dead pedal at the top. When I lightly pushed back on the slave bearing, I discovered that my system came to rest with the slave piston 0.116" BACK off of the bearing. My 2" of pedal travel was what it took to move the slave piston the 0.116" until it came into contact with the TO bearing. The only other "symptom" I had was a little bit of fluid that was appearing behind the master cylinder's boot inside the car (a couple drops).

I was advised at this point to rebuild the master cylinder. Did that, bled/filled the 2 sections, hooked up the master to the line to the slave, and its a complete repeat of the same scenario. Starts good and degrades to 2" of dead pedal after about the 30th (for the heck of it) slow pedal strokes... and I'm talking SLOW.... 10 seconds down type of slow.

So it occurs to me, how can the slave piston be getting PULLED away from the TO bearing? Where's the vacuum coming from?!

I had set the pedel heim joint connection to give me full "backward" travel on the master cylinder when the pedal was up like my instructions advise that I do. Looking at the attached pic, I've got the guts of the master with a sketch. The seal is pushed by a "slug" with an O-ring on the other end. The only way I think I can get a vacuum developing in the system is if the piston starts off too high, so that when it comes back up, it ends up pulling a vacuum against the reservoir after uncovering the resevoir feed holes. What I did was to adjust the master cyl such that its about 1/8" away from returning all the way to the top. I used a vac/pressure pump and a "ball" fill tube that fits into the top of the resevoir cap. I adjusted the top end travel of the piston in the master downward until I could no longer "pull" fluid w/ the vacuum pump back up into the reservoir. At that point, I started moving the adjustment slowly back (letting the piston come up higher in the master), until I can still "pull" fluid back thru the system into the reservoir, and then push it back into the system FROM the reservoir. This should've put the seal lip in the master just on the reservoir feed holes. This has given me a pedal that feels just like the daily driver, and I can't make it drop by dorking around with the pedal like I could before. Popping the sideplate off the scattershield, it looks like I've got about 0.020-0.030" of travel of the bearing to go back before it hits the slave piston internally. Clutch grabs right at the top.

Thoughts? I'm waiting for it to blow up now.
Jeff

you would get a vacuum in the system if the cap of the master wasn't vented, which it should be. the seal is supposed to uncover the hole to the reservoir. i will ponder this further and see what i come up with.

bttt for you.

Without beating around the bush.... their original design sucked.

I paid for their new master (Wilwood), adapter and line with the bleeder. Problems gone.

I think they should have recognized the problem and recalled their original design. I'd be cruising around and lose pedal without notice and I wasn't alone.

I do not recall your measurement of 3.71 but that IS NOT going to work. When you take your bell to finger measurement and subtract 3.325" from it, you need to have a final answer of between 1/8"-3/8". Your answer is .385 which is outside the .375" max limit. YOu need another 1/4" spacer to bring it back within spec.
That is your first issue. Secondly, it is probably air-locked but with the measurement being out, you need to correct that first.
You e-mailed me over the weekend and I will point all of this out again in your e-mail but you need to get the limit back under 3/8" to start with.


Richard
Tech Support

You guys are friggin' amazing... Check your inbox (10/3/07). I emailed you all my dimensions, noted how they were over the spec you gave me, and asked for an ETA on a new set of spacers. We spoke on the phone after that and you had my #'s blessed by someone and said "put it in", so now its "take it out"?!?!!?

Sorry, I don't have e-mails still in my inbox from last October.....

Once again, I would not have told you that a measurement of 3.71 was good. I don't know who told you that but it is wrong. Leave it in if you want and it will not work, in fact, it'll blow the face off of the bearing, or, give me a few days and when you receive the 1/4" spacer, install it, put it back together, bleed it and be done with it.

I do need to know what color the front retainer is though? It is either black or billet. Also, is the bearing bolted on with 1 bolt and a standoff spacer or 2 bolts? I need to know which setup you have so I can send the correct style spacer.


Richard

To try keeping this constructive, what is the right spec here? Or are there now 2 different single line bearings? Everytime this has come up, I see 3.5-3.625" noted as the clearance, and using what you just said, now its 3.45-3.70"? Please don't send me a 1/4" spacer, cuz I'd be nuts to put that in and drop my clearance to 3.46". That's below the original spec, and when the clutch disc wears, the fingers go back more, so I'd be under 3.45" in nothing flat. You have all my measurements/specs. If we're going thru this, please send me something that puts me in the middle.

Who makes this slave cylinder? I'd like to get the complete specs on it. In particular, what's the max recommended extension.

Does the wilwood mcyl have a custom flange welded on like the CNC or is there just a firewall adapter arrangement?

Jerry, the more I think about what I did, and with your comments, I now have no idea why that helped. I still can't think of a scenario that ends up pulling the slave piston off the bearing (at least any reason outside of Brian's comment).

Funny revelation too. I learned something else interesting when rebuilding the master cylinder. My original rev 1 kit's mcyl developed a TERRIBLE habit of not wanting to return to the top of the travel. It'd always hang up about 1/2-3/4" down in the bore and you'd have to bounce the pedal to get it to come back up (if you were lucky enough to get it to come back up). I'll bet whoever put that puppy together had the spring in backwards. With the open coil end driving the seal instead of the alum "slug" end, it'd probably bind up like that. That's the only explanation for it now that I saw the guts of it. I wish I still had it to pull apart.

Jeff

O.k., when you take the bell to finger measurement, in your case, you said 3.71". Then you subtract 3.325" from that and the answer you get needs to be between 1/8"(.125) and 3/8" (.375). With a 3.71" measurement, the answer is .385" which is just outside the spec. If I send you a 1/4" spacer, that will drop the final answer to .135" which obviously is at the low end of the range but still good.
I have to believe that the system is still air-locked though. With a .385" answer, you should be able to get a pedal although, it would be close to the floor.
In you e-mail to me, you stated that you have the black modified retainer. Because we don't use that setup anymore, I will send you a new complete lower end setup including a new bearing, retainer and three 1/4" spacers. It will be pre-assembeled so you can see how it is supposed to go together. BEFORE you re-install it, double check your measurements one final time.

In the e-mail you sent last night, you stated back in October that you had 3.67-3.71. 3.67 is in range, all be it, the high side. 3.71 is out of range.

I will be sending it overnight to you today. Let me know.


Richard