Recently I've experienced some weird clutch issues... lets all brainstorm...
Let me start with the history... grab some coffee or energy drink for this story!
Sorry for the lengthy post... but this situation requires major detail to fully understand/picture what I'm going through.

HISTORY:
Started several weeks ago when I decided to replace the transmission with a used one because I was having difficulty shifting.
The condition of the transmission was unknown because the vehicle was in a front-end collision and totaled.
The owner stated that the transmission shifted fine... that is all we had to go off of.

When it came time to swap transmissions, I also decided to replace the pilot bearing and oil seal.
A local guy offered to give me his stainless steel clutch line (never used) and figured with the transmission down, it'll be the perfect time to change the line.
So with the transmission down I removed the pressure plate and disc so I could use the slide hammer to remove the pilot bearing.
With the pilot bearing and seal removed, I noticed 20% of the seal was torn and further up on the e-shaft (past the pilot bearing).
I installed the new bearing and seal using MazdaTrix's installation tool.

Since I had the HD release bearing from BHR on my old transmission, I transfered that over to the used one.
The bearing still felt great and I lubricated the required spots (including the input shaft).
The pressure plate and disc is the Stage 1 Exedy and the flywheel is the BHR/Spec one, which there was nothing visually wrong with these components.
I installed the stainless steel clutch line and lastly, installed the transmission and other components.

First thing I did was adjust the clutch pedal stroke and free play to spec.
We bled the line multiple times and the pedal still felt soft for the first few pumps, then it got stiff (no sexual jokes required).
The car was still up on jack stands so I could put it into gear and see when the wheels start spinning.
When I started the car, I couldn't get into any gear!
I moved the pedal's push-rod out a couple turns at a time while trying to get into gear... no luck.
We went through 1/2 a bottle of brake fluid trying to bleed this thing and it wasn't getting better.
It was getting late so we called it a night and slept on it.

Next morning I woke up and decided to try it again, starting with adjusting the clutch pedal back to spec.
I also inspected the clutch pedal assembly to make sure there were no cracks/fractures (even though my pedal is welded).
Once I did that I started the car and to my amazement... it went into gear!
My engagement point was between 3-4" down the pedal stroke.
We all shrugged our shoulders and was pretty happy... it was a hot day, we were sore, and didn't feel like dropping the transmission again.
I drove the rest of the day with no problems.

NOW THE PROBLEMS (and confusions) BEGIN:
The next morning I started the car and quickly realized the pedal felt soft.
It took almost 3/4 the pedal stroke before I felt major resistance.
I moved the pedal's push rod out and realized how easy it was to turn into the master cylinder.
Once I felt resistance from turning, I tried to get the car into gear.
I was then able to get into gear, but my engagement point was almost instant (as soon as I let-up on the pedal).
Driving around I noticed the pedal had some "free play" or softness for the 1st inch of travel.
Weird thing is... after about 10min of driving, the pedal got really stiff all the way up top and I no longer had the softness.
In fact, I had no pedal free play whatsoever which I don't like because then the release bearing is constantly riding on the pressure plate.

Another weird occurrence is when the pedal felt stiff through the entire pedal stroke, I experienced a strange feeling at higher RPMs.
Once I was above 4K RPM, I would begin feeling the soft pedal response.
And the higher up in RPM I went, the more soft pedal travel I had.
If I quickly let off on and accelerator and let the RPM drop to 4K or under, the pedal stiffness was back to the full pedal stroke.

Next morning I tried to drive off again, but when I started the car, I once again couldn't get into gear.
And once again I had to move the pedal's push rod out just to get it into gear!
This occurred for several days and it got to the point where I couldn't move the push rod out anymore.
Then one morning I realized if I started the car and waited for roughly 5 minutes, I would be able to get the car into gear.
Then, once I started driving for a little bit, I would get my stiff pedal feeling back.

That weekend I decided to trying bleeding the clutch again.
I watched the hose carefully to ensure nothing was going back into the slave cylinder while the other person in the car was picking the pedal up.
The first couple pumps of the pedal it stayed down and required manual assistance to bring it up, but every pump after that it returned itself.
We did this a good couple dozen times before calling it quits.
I moved the pedal's push rod back out knowing it was in pretty far and drove it around without any problems.

The next morning... it came back... soft pedal response 3/4 down the stroke and couldn't get into gear!
Knowing that I would constantly chase the push rod out, I decided to let the car "warm up" like before and see if the pedal got stiffer.
After about 5min it felt stiff again and i was able to get into gear, but the engagement point was still near the floor.
I dealt with this until the following weekend.

Charles R Hill referred me to a TSB for difficulty disengaging the clutch:

Seemed like a good place to start, so I got a used slave cylinder (from the wrecked RX8) and took it apart to give it a good cleaning and lubricated the seals.
I then installed the slave cylinder and bled the clutch.
It appeared to be OK... but I wasn't going to know until the morning (when it seems to give me the soft pedal for the 1st 5min).
Diving around I did notice that I still had the RPM based issue where the higher in RPM I went (above 4K RPM), the more soft pedal I experienced.

The following morning... same problem!
I started to think outside the box and recalled an issue with some LS1 Camaros and Corvettes with their stainless steel clutch line.
Their line had a restrictor installed at the fitting to soften the "hit" and reduce abuse on the drivetrain.
Problem is with a restrictor, when the pedal is lifted, it takes longer to fill the master cylinder.
So these guys were drilling out the restrictor.
This was probably a long shot for my situation, but I did install a SS clutch line and it was a variable that needed to be ruled out.
I reinstalled the OEM clutch line, bled it, and drove it around.
Strangely... I didn't seem to have the "RPM based" issue.
But I waited for the following morning to see for sure.

Of course the problem returned... soft pedal for 5min upon start-up.
This time I got a used master clutch cylinder (again, from the wrecked RX8) and took it apart, cleaning it up, and lubricated it.
After that I installed it into my car, bled the clutch, and drove it around.
It felt fine (like all the other times) so I waited for the next morning.
Next morning came around... and the problem returned!

BRAINSTORMING TIME:
Obvious since I've replaced every hydraulic component, the next plan-of-attack will be to drop the transmission and look for anything unusual.
But the symptoms point to two different areas.

1. My pedal softness seems to point to something in the hydraulic line, but that was all now ruled out.
   Bleeding it 5 times now and watching the clear hose for fluid/air to reenter, I'm pretty sure its not air in the line.
   Plus, if there was air in the line, my pedal wouldn't get stiff after 5 minutes.
   But why does "warming up" the car for 5min appear to help and what component (if not hydraulic) could be affected by temperature?
2. The weird RPM based issue where the higher in RPM I go, the more pedal softness I experience, points to something within the bell housing.
   But nothing within there matches the symptoms I have.
   The pilot bearing was replaced, but that just supports the input shaft in the e-shaft and shouldn't effect clutch operation.
   And the transmission shouldn't really effect the clutch much since the only thing common is the release bearing rides on the input shaft.
   If the clutch disc was installed backwards, I would notice some unpleasant noises.

I still need to plan a day to drop the transmission and give it a good look-over.
But this is going to be one of those times I'm going in there blind with hopes in finding something unusual.
This would be my 5th time dropping an RX8 transmission, so I wouldn't call myself a noob at it.
And I've bled my clutch in the past with no problems.
So any ideas on which component would be causing this kind of weirdness?
I'm pretty much open to any theory at this point!

Thanks for reading!

 

subscribed for reading later, im tired... haha its late here, ill read it later Jon, I dont want to forget about this

 

Ha... no problems...
This read will require much rest or else it'll put you to sleep

 

Jon, I cant offer any help, but, when I installed the F1 S3 6 puck clutch, I had similar problems ,after the install I had no resistance at the peddle which went to the floor and stayed there,I noticed there was about 1" space between the slave cylinder pushrod and the clutch fork,so I adjust the pedal push rod and was able to change gears,although the amount of pressure needed was about half of what the OEM clutch was, its very soft.When I push the pedal (it has the required freeplay)the clutch starts to engage around 1" after free play ,but when I release it, I only have to move the pedal 1-1/2" from the floor and the car shoots off like Ive dumped the clutch, and when I shift at 8k or more ,the pedal stays on the floor. I was thinking of making an adjustable slave cylinder push rod to see if it helps with the pedal travel.Yes, I know the 6 puck is different from OEM, but I know this is not "normal".

 

FastFreddy61- I have exercised the thought of there being a gap between the slave cylinder push rod and the release fork... but couldn't make much sense of it.
Rebuilding the slave cylinder (noted in the TSB I linked in the 1st post) was to help with the ethonal issue during manufacturing where pressure would build-up and create a gap between the push rod and piston.
Since I have an extra slave cylinder, I guess I could cut a couple slits in the boot to relieve pressure (if any is generated) and see what happens.

But with this theory, why would I have to wait 5min before the pedal is stiff again?
And why would this be affected by high RPM?
Sucks that the cylinder is in such a shitty location and I can't easily see if there is a gap.
Like I said... I'm all open to ideas and theories...

 

Broken Clutch Pedal bracket? Also your year is missing from your Goodies list. So you have an extensive and informative write up but your baseline is missing (year, model .. basics). It does sound like it was either the early slave assembly fluid TSB Or the broken bracket or a pressure plate / throw out / linkage issue.

 

Was the throwout bearing sticking on the input shaft?

This was the same flywheel and pressure plate and disc as before?

 

Nope... had the pedal out several times and inspected it closely each time

Didn't think it was relevant to my problem... but since you asked...
Its an '04 GT with 51K miles and I'm the original owner.

 

Nope... I lubricated the input shaft and cycled the release bearing and fork back and forth.
It felt smooth with no resistance.

Yup!

 

I would never expect it but sounds very similar to the problem I'm having its ironic that we posted at the same time. I'll be following your thread hopefully we both get to the bottom of this

 

Jon,
Mailing this one in from deep left field, but...
Failing everything else you have done/redone, could at least a contributing factor be the brake fluid itself? I know you went through multiple bleed cycles and must have consumed a lot of fluid doing that, but if it all is either from a bad batch of fluid (picked up water, other contaminants, or was formulated wrong by the manufacturer) then some of the issues your having at temerature might be explained by improper thermodynamic performance of the fluid.

 

VOODOO8- I tried two different bottles of fluid, same type and manufacture, but different date code (or assuming so since they were purchased at different times).
Its Valvoline (dot 3 & 4) fluid that I've been using for awhile (even prior to this problem).

 

ive seen the pressure plate issue in a few other posts, and to add to it some people at rpms in excess of 8k seem to have zero pressure on the clutch and it sticks to the floor. So im going to point at the pressure plate and figure it has to be something going on there...

 

Hey Jon...when the car is cold...is there play to the release fork or the push rod? While you have replaced the entire hyrdolic system it should show us which side of the system is weak/failing/whatever.

 

Hard to tell without jacking the car up and reaching up to the release fork.
And I tend to have this "free play" in the early mornings after work, so doing this in their parking lot isn't ideal.
There have been a few suggestions/ideas from people that I'm considering...

 

This would also show in braking performance, which hasn't been affected, right?

 

The Doc has a point there...

 

I can't remember. When you put the tranny in...did you use your old release fork or the one off the donor? Maybe in the accident it was bent funny?

 

I think in situations like this it's good to step back and look at the differences between your two transmissions. One has been in a accident while the other has not, I think this inlies where the problem is. So something with the accident transmission is different than the new one, just my .02 cents. I know this doesn't help much but I'm trying

 

I know that the tranny swap was done because of the old one being on it's way out.

 

The only thing the transmission has in common with clutch operation is its input shaft since the release bearing rides on it.
Yes... this tranny came from a vehicle involved in a front-end collision, but keep in mind that the donor's motor was installed in another car and ran great.
The transmission's input shaft inserts into the motor e-shaft, so I highly doubt it has anything to do with it.

The release fork is also from the donor's transmission.
Bending the release fork in the accident is far fetched (I would even go as far as saying impossible), but I appropriate the "out of the box" way of thinking.
Its good to think that way (within reason) on situations where the obvious isn't evident.

 

Could you please state the outcome. Clutch, clutch master, slave, etc???

 

Sure... I know I've been absent from this thread while I tried/tested various theories.
I wanted several weeks of driving/testing to verify the change made a difference.

First thing I did (where I left off above) was cut a few slits in the slave cylinder boot.
This was to test the theory of pressure buildup (from ethanol) separating the piston from the push-rod.
My issue was if I let the car sit for several hours, I couldn't get into gear because of the excessive pedal free play.
This was also repeatable every morning as the temps outside were colder.
Since I cut those slits on the boot... I have yet to experience a problem where I couldn't get into gear.
Now... as you probably read above, I tore apart the slave cylinder and cleaned it up hoping to rid any traces of ethanol.
So this tells me that the best plan of action would be to buy a rebuild kit (new seals and boot) or just buy a new slave cylinder.
I plan on buying a new one next spring (no reason to rush it now with winter approaching).

Then for the RPM-based issue.
Last week I reinstalled a used OEM clutch to test a theory with the pressure plate.
With the OEM style clutch installed, I still notice the increased pedal play at high RPM... but its not as easy to identify.
With the aftermarket clutch having more clamping force, it was easy to tell while the OEM clutch being so soft made it almost unnoticeable.
When I get a chance, I want to drive another 8 that hasn't had any clutch work done and see what happens.
I'm starting to think this isn't really a problem (far as clutch operation), just more noticeable with certain clutch/flywheel combos.

Thanks to Ray for brainstorming with me on this.
I learn a little more each time we talk
Ray- feel free to add anything to this topic if you wish.

 

Ill be out that way Sunday for an AutoX if you want to borrow my car Jon. You can either stop by Geauga Lake or I can swing by on my way home if you want.

 

Geauga Lake is only 10 minutes from my house... I can probably just stop by.