Clutch pedal height irradic. Stumped here..

[flexnuts02]

So I am a fully certified tech with my dad in our own private shop. This issue has slowly come in ever since I installed the new shep trans.
Other parts included brand new clutchnet sprung disk and new ACT flywheel. Re-used my good looking ACT 2700 pressure plate. New throwout and greased EVERYTHING involving clutch fork movement.
My trans started to grind as the revs were higher on a warmed up motor.
Clutch was always adjusted right on this car and I just replaced the master and adjusted as per jacks transmission video.

So once the car is warm and I spool 5psi through like 6k rpm moderate throttle, the clutch pedal height is much lower to the floor than when the revs are lower for daily driving.
*It does seem like when the pedal height fades out, you can pump it twice to regain the pedal.

My theory is that it's due to the crank pushing inward when oil is hot and the revs are up.
When the revs are low it appears to not ever move the crank.

And THAT is why I don't get it, wouldn't a 2700 pressure plate move the crank regaurdless of the RPM? How could the crank hold up to the pressuyre plate at idle and then give way when the revs are up?

We measured the movement on the crank pulley with a calibrated dial indicator, we came up with .099ish which is apparently right on the edge of spec as per ShopKey5.

Now I did not build the motor so depending on the sizing for thrust bearing specs, maybe this is the way the motor was even when it was fresh and perhaps this issue is a mechanical clutch issue.

I just don't see how it could be a mechanical problem since it seems so much like the crank is moving when you feel the pedal is gone randomly.

Ask me any questions!! I don't wanna build my first race motor just yet if I don't have to!


EDIT: The car is a 98 swapped AWD with an entirely built 1g longblock. Maybe 8k miles on the longblock. Big turbo big fuel.

 

[Black-Out]

So I have a few questions...
1. Have you checked or replaced the clutch master and slave together as a couple yet? (internal leakage concerns which can cause the old part to fail if only one is replaced)

2. Have you checked for leak trails on the Floor boards of the car by the pedal assembly?
(failed or failing master assembly)

3. Have you tried flushing and re bleeding the hydraulic system yet? (contaminated fluid)

4. Does your clutch system have a proper clutch fork?

I highly doubt that your experiancing anymore crankshaft movement at higher engine speeds than at idle but this is a very odd issue, I've never come across (or thought it possible) from a mechanical stand point. If you have the correct clutch fork in the car (because some dsm clutches do require an offset fork for proper clutch operation after an after market clutch has been installed) and the hydraulic system is in good order then the only thing you need to inspect from there is the actual pedal assembly (of which I have seen crack and break around the securing points of the bulk head due to the additional pedal pressure produced by higher clamping force performance pressure plates. I've seen the metal begin to tear away and everytime you use the clutch pedal the effect continues to worsen until you can no longer disengage the clutch...I've seen only 1 case where the pedal had come off completely while driving.

Check these things out if you haven't already as they may be some hidden failure you may have overlooked despite your experiances....Good luck sir!

William-

 

[Artago]

Pressure plate cracked? Had something similar happen to me... see here.... (Pics at bottom)
http://www.dsmtuners.com/forums/drivetrain-tech/380441-clutch-soft-suddenly.html

 

[Black-Out]

Pressure plate cracked? Had something similar happen to me... see here.... (Pics at bottom)
http://www.dsmtuners.com/forums/drivetrain-tech/380441-clutch-soft-suddenly.html

Never seen a failure like yours either........So I take it the pp cracked beneath the cover so it wasn't outwardly visable?

 

[BoxheadTim]

So once the car is warm and I spool 5psi through like 6k rpm moderate throttle, the clutch pedal height is much lower to the floor than when the revs are lower for daily driving.
*It does seem like when the pedal height fades out, you can pump it twice to regain the pedal.

That aside suggests to me that you probably have an issue with the clutch hydraulics.

How old is the fluid? Any leaks? Have you recently bled it? How old is the flexible hose?

 

[SrKegler]

If you can regain pressure/pedal heigth by pumping the clutch it means you're losing pressure someplace in the system. I'd start with the slave cylinder and work my way back. It doesn't take long to blow out an old slave with a performance clutch. I go thru about 1 new cylinder a year myself with an ACT2600. Started keeping a spare one in the trunk.

 

[Artago]

Never seen a failure like yours either........So I take it the pp cracked beneath the cover so it wasn't outwardly visable?

Exactly, it wasn't visible. The only thing I noticed was that 2 of the PP fingers were farther apart than the rest. So I sent it to ACT and they took it apart and discovered it was cracked.

 

[PieEyedPiper]

Rebuild both the slave and master. Go from there - chasing these problems is why I have less hair.

 

[Artago]

Rebuild both the slave and master. Go from there - chasing these problems is why I have less hair.

Agreed, start with something easy to check/fix and go from there.

 

[flexnuts02]

Artago, I too hope its the PP but from the behavior i can just see/feel what i experience and it gets me feeling gloomy .

The slave is the only hydro possibility as the fluid is always newer than the engine oil . Master is new now and there are NO rubber parts in the hydro system.

*Just seems odd that the only factors in this issue include warm engine oil AND revolutions per minute and that, to me eliminates the entire hydro system. Which would point to the crank other than the actual plates themselves dealing with the rotating and outward gravity but I would be VERY surprised if this is mechanical, after knowing the symptoms and having as much experience as I have had in working on every car you see on the streets, everyday.*

I threw in this aftermarket master quick to eliminate the master, ill have them send me the slave today to throw that in, HOPEFULLY I won't be returning the new slave cylinder that I get today if you know what I mean! I'll post back!


EDIT: Ya know what, the slave is a waste of time..

The fact that I can sit in the car at idle or with the engine off, and pump pump pump pump pump pump pump the clutch and NEVER have it show anything tells me the hydro is fine.

Now think about when I rev out moderately to 6k at 5psi, imagine your clutch height lowering to the point that you feel it get hard, but the floor is right there, so you can't quite go far enough to get the full disengagement..GRIND.. CRANK was pushed back
OR
The clutch plates malfunctioned in some way. Looks like I almost have to pull the trans as step one, right?

As a professional, thats my equation..

 

[Gasolinebaptism]

I'm experiencing the exact same issue.. Haven't looked into it too heavily as it's on my DD that might see 4k rpm once a day.
But I have the exact same issue, I however haven't noticed it being worse with warm oil... I feel like it's a constant with high RPM.

 

[flexnuts02]

I'm experiencing the exact same issue.. Haven't looked into it too heavily as it's on my DD that might see 4k rpm once a day.
But I have the exact same issue, I however haven't noticed it being worse with warm oil... I feel like it's a constant with high RPM.

True, maybe its because I dont take the revs up until the oil thins more.. I use 15-50 synthetic. I really hope it's mechanical cause the only thing it could be is the PP, the rest is still in warranty and the flywheel is a no brainer, cant be that.

 

[Gasolinebaptism]

It's got me stumped too, and I've never been stumped by anything with a car...
I've always took pride in my diagnostic skills, it just works for me... But I hear this issue and think... "WTF?"

 

[babyviper]

I had this problem happen to me, I got a new clutch installed along with a brand new master and slave. The guy at the transmission place stated that the turbo master wouldn't work and he used the N/T one instead. This continued to happen and it was all related to the master. I would say replace your master and see what happens. It's cheap and it is good to replace the fluid on a regular basis which probably neither has ever been done.

 

[PieEyedPiper]

What's the story with your endplay? Spec is like .003 to .007

Source: not shopkey5

EDIT: Oh and btw, it most certainly IS your hydraulics if you're sporadically losing pedal pressure. The pressure plate won't just have moods where there is pedal and then no pedal. But hey, I'm just a guy whose been through it a few times.

Let us know what you find. And please recheck your endplay cause if that's an accurate measurement your shit is walked.

 

[Gasolinebaptism]

What's the story with your endplay? Spec is like .003 to .007

Source: not shopkey5
)

Let us know what you find. And please recheck your endplay cause if that's an accurate measurement your shit is walked.

+1 haha.
I have the problem going on with no clutch at high rpm.. can't explain it, but It's got to be hydraulic. End play isn't causing it.

 

[PieEyedPiper]

+1 haha.
I have the problem going on with no clutch at high rpm.. can't explain it, but It's got to be hydraulic. End play isn't causing it.

When I had my Spec Stage 2+ I would perceive a light pedal at high RPM, too. I was also fighting inconsistent pedal.

My clutch was not adjusted properly and I had waaaay too much throw. This actually started re-engaging the pressure plate - what I perceived to be a light pedal. And no wonder I thought I had what seemed like multiple engagement points - I did, essentially.

 

[flexnuts02]

I adjusted mine as Jacks trans says on youtube, this is the only time ive done this and its got alottt of throw when you adjust it like they say to. I used to always just adjust it off the floor just enough that it wouldn't drag in gear.

The master is brand new, fluid as well, slave is newer and not malfunctioning as the slave cannot malfunction and not show it.

The endplay is certainly too much. It's gotta be that.

Both the older master (which was still pretty new) and the currently BRAND new one didn't change a thing! So provided that I DO know how to adjust a hydraulic clutch and NEVER had this issue in my 6 years of wrenching/daily driuving this car, it is pointing me right back to the endplay.

I dont know what else to do other than snag the trans out first, to make sure there isnt something showing with the PP. And then when I find nothing wrong like I know will be the case, I'll be tearing the block out to see if I can re-use it or start over with my other block here thats never been machined and build my OWN race motor, correctly for the first time of this cars 3 race motor career!!

Why the DUCK can't anyone freaking blueprint and balance a crank shaft install properly!? These things are SIX bolt motors for crying out loud. This marks 2 walked 6 bolt motors, and the stocker 7 bolt still runs in my friends car with 150k miles on it. What the hell causes these six bolts to walk? Idiots grabbing blown blocks and having them built for race?

And piepiper, come down to philly for me. I'll have you staring at the engine bay like this after we discuss the issue in person, and you get to feel it in real time. The fact that the pedal height is suddenly LOWER but NOT different than normal. The hydraulic pressure only changes in my eyes because of the crank position, so technically I'm saying that the hydraulic pressure is good even when the issue acts. Know what I mean? Just as if I re adjusted my pedal height and DIDNT tap the hydro pressure in anyway.

 

[PieEyedPiper]

Wish I could, my friend. Helping DSMers is what it's all about.
Let us know what you end up doing with it, sucks you've had 2 6er's walk...kinda weird odds, no?

I adjusted mine as Jacks trans says on youtube, this is the only time ive done this and its got alottt of throw when you adjust it like they say to. I used to always just adjust it off the floor just enough that it wouldn't drag in gear.

The master is brand new, fluid as well, slave is newer and not malfunctioning as the slave cannot malfunction and not show it.

The endplay is certainly too much. It's gotta be that.

Both the older master (which was still pretty new) and the currently BRAND new one didn't change a thing! So provided that I DO know how to adjust a hydraulic clutch and NEVER had this issue in my 6 years of wrenching/daily driuving this car, it is pointing me right back to the endplay.

I dont know what else to do other than snag the trans out first, to make sure there isnt something showing with the PP. And then when I find nothing wrong like I know will be the case, I'll be tearing the block out to see if I can re-use it or start over with my other block here thats never been machined and build my OWN race motor, correctly for the first time of this cars 3 race motor career!!

Why the DUCK can't anyone freaking blueprint and balance a crank shaft install properly!? These things are SIX bolt motors for crying out loud. This marks 2 walked 6 bolt motors, and the stocker 7 bolt still runs in my friends car with 150k miles on it. What the hell causes these six bolts to walk? Idiots grabbing blown blocks and having them built for race?

And piepiper, come down to philly for me. I'll have you staring at the engine bay like this after we discuss the issue in person, and you get to feel it in real time. The fact that the pedal height is suddenly LOWER but NOT different than normal. The hydraulic pressure only changes in my eyes because of the crank position, so technically I'm saying that the hydraulic pressure is good even when the issue acts. Know what I mean? Just as if I re adjusted my pedal height and DIDNT tap the hydro pressure in anyway.

 

[Darris]

just taking a stab at it. does the little rubber hose between the resisvor and the clutch master cylinder have a leak by any chance? i had the same problem, and that was my issue

 

[flexnuts02]

The problem disappeared! I started daily driving it again, frustrated that I couldn't decide what to do next.

Took it to the DSM vs Subaru in Englishtown with some philly heads and ran an 11.7@125. Still driving it and the pedal is flawless! I love it having so much throw now that im used to it and it works correctly.

Must have been the flywheel/PP/disk.

PS gonna recheck the crank runout soon too. See if it got any further out of spec, still gotta keep an eye on it.

 

[9thgencorolla]

Flex is this a 2nd gen? Your problem is in what this guy calls the fcu. Take a look at the 2nd picture.
http://www.dsmtuners.com/forums/articles-drivetrain/314295-how-install-ss-braided-clutch-line.html
I had the same problem in my 2g. Replace master and slave still nothing. It would happen after driving it for a while (sort of like driving on the highway.) After about 3 months of this crap. I said the hell with it and tried the ss braided clutch line. From there on out never had a issue. Hopes this helps!