Clutch issue-not disengaging, in spec

[3D914]

Been getting my son's 924S running and hit a snag with the clutch. Already replaced the slave, master cyls, and rubber hose between. Checked clark's page and measured the travel. It measure 17.5-18mm. Haynes says min is 15mm, so I should be good.
Looking in the inspection port with the pedal depressed, the arm gos all the way forward and just touches the bell housing. I have adjusted the pedal rod as needed with very little free play.

With clutch in (not running) it will shift no problem between gears.
With clutch in (engine running) get a little grinding and have to push the pedal to floor.
With clutch in (engine running) in first gear, and press on break, idle drops and engine dies. Hear a pronounced brushing sound (not metal grinding).

Recently installed the engine, used clutch disk (in spec), and splines had only minor wear. Fork didn't appear bent, but don't have specs to verify any measurements.

Is there anything else that can be checked before I pull the tranny to help identify problem?

TIA,

[mikepellegrini]

Perhaps it's not fully bled? Sometimes it's a real PITA to bleed the clutch because the fluid intake is relatively high in the master cylinder resevoir.

[Grandad#3]

This is the time you need a Motive Pressure Bleeder. It is well worth the money spent.

Cheers,
Larry

[3D914]

Thanks guys, but its not the bleeding. If I'm getting full extension on the slave cylinder, and its just touching the forward part of the bell housing, and the travel is in spec, then it something more. Just trying to isolate what the possibilities are.

[3D914]

One possibility suggested was "Disk in backwards? T-out bearing in backwards?"

I can't be certain how I verified disk direction - so that's an unknown.
The throw-out bearing though - I don't see how that would even assemble if in backwards.

Does anyone have a dimension stackup on the clutch components that might indicate the effect of putting the disk in backwards?

[carsonmx114]

You didn't mention if this problem has just started or if it has been like this since you had the engine out. I can't remember for sure but I don't think the disc will go in backwards because the damper springs will hit the flywheel bolts before the disc touches the flywheel, but that was my first thought also. When I was a teenager I had a VW rabbit and the disc stuck to the flywheel. I tried everything I could think of but I couldn't get the car in gear. I then decided I would pull the transmission out to find the problem. I unbolted everything down to the cv's and realized I didn't have a 12 point allen for the cv bolts so I bolted everything back together and to my suprise my clutch worked... I now know that by wagging the trans around I broke my stuck clutch disc loose. I should have just started it in gear and held all three pedals to the floor. That story makes me smile...15 years old and no clue what I was doing.

[HondaDustR]

Originally Posted by 3D914

With clutch in (engine running) in first gear, and press on break, idle drops and engine dies. Hear a pronounced brushing sound (not metal grinding).

Is this with the car moving?

What if you jack up one of the rear wheels with the other wheel still on the ground, put the transmission into 5th gear, and try to move the wheel while the clutch is pushed in to see if it's dragging or simply not disengaging at all. What does it feel and sound like if it does move? The release fork could be bent, but the fingers that contact the release bearing could be worn as well. How is the release bearing? If it's not new, it could be failing. The thing is, any slack in the release bearing or release fork pivot shaft and bearings would just be compensated by the hydraulics and it sounds like you are getting enough travel from the slave cylinder. Any grinding noise when the clutch is disengaged is likely release bearing related. Was the pressure plate replaced, and if it was not, were the spring fingers in good shape and not showing any wear or grooving where they contact the release bearing?

Hehe...post number 1987, same year as my car.

[3D914]

OK some added info. IIRC from assembly, the release fork pivot shaft & fort were a good fit. No binding, but not excessively loose. Some wear on the bearing portions of the arm - corners were radius'd and a little worn - but this seemed by design. The arm could have been bent a little and not seemed out of place. A lot and I would have questioned it.

Release bearing was in good shape & didn't appear to have significant wear. Not sure what slack there would be other than radially. Honda - can you elaborate?

With engine running & in first gear, I press on break & clutch - idle drops and engine dies. Hear a pronounced brushing sound (not metal grinding).
I'll try the manual rotation of the rear wheel to see/hear the effect.

Thanks,

[carsonmx114]

I'm guessing the noise you're hearing is the key to the problem you're having. I'm thinking that the flywheel/pressure plate is still contacting the clutch disc somehow. This of course is not good news because you're gonna have to go back to square one. Did you change any of the clutch components, or have this clutch disc, throwout bearing and flywheel worked together before? If one or more of the parts are different I would guess something is staying up against the disc because of that part.

[HondaDustR]

Originally Posted by 3D914

Release bearing was in good shape & didn't appear to have significant wear. Not sure what slack there would be other than radially. Honda - can you elaborate?

With engine running & in first gear, I press on break & clutch - idle drops and engine dies. Hear a pronounced brushing sound (not metal grinding).
I'll try the manual rotation of the rear wheel to see/hear the effect.

Thanks,

Well, the release bearing is basicly a thrust bearing, so smoothness and play in the axial direction is the most important.

It sounds like something is stuck or binding somehow. Always a good idea after getting the bellhousing and drive tube bolted up to have someone hold the clutch in and you rotate the driveshaft to ensure it releases correctly. That way you'd catch any problems before spending a few hours getting everything else back together. The shaft will turn by hand easily if the clutch is releasing correctly. Hate to say it, but there's a good chance you'll have to go back in. You're getting well within spec release travel, and it's hydraulic, so any play should be automatically taken up by the slave cylinder.

[JShep]

Based on the other responses and my own experience, I would suspect that the clutch disc is not freely moving on the splined prop / drive shaft, not allowing it to disengage fully / completely. In other-words, the clutch disc is not moving forward / aft on the shaft, even thought the pressure plate is moving into the "disengaged" position.

To get to these parts, a disassembly may need to be completed.

[carsonmx114]

Ok, I just re-read the original post... It's hard to imagine that there's enough drag to stall the engine but enough slip to put it into gear with only a little grinding. Doesn't that seem strange?

[3D914]

OK did the 5th gear, one wheel on the ground, clutch in test and there is definitely a clanky/grinding noise when the rear wheel is rotated - so there is must be interference at the disk.
So it looks like I'll be going back in ;(

[914efi]

I had a similar problem on a 911, mine was intermittent. When I took things apart, I happened to pick up the PP and a loose ~12mm nut fell out. It was a used PP and I guess the nut had fallen in and it was enough to keep it from moving when it got into a certain position.

[3D914]

OK finally got the tranny out & everything off. After 6 weeks, smashing my hand, and spending 6 fr&^$#@king hours getting the bell housing off! Fortunately, there were no surprises during disassembly and no spare parts fell out.

Here's some pics of the parts.
Flywheel:


New plate (forgot I bought new instead of the used):


Existing pressure plate:


Existing Release lever:



Existing Release bearing:


Visual inspection doesn't indicate any severe failures as far as I can see. If you zoom in on the disc plate springs at 3:00 & 9:00 o-clock you'll notice they were hitting on the flywheel bolts. I did have installed correctly as that is the flywheel side. The disk surface doesn't look like its been touched at all. I would expect to see some marring.

The pressure plate spring arms don't appear to have excessive wear. The bearing spins freely with no axial play while spinning. However, there is 3mm of axial play between the bearing and the spring arms.

The release lever doesn't appear to be bent - but without some dimensions to check or pictures of a new one to compare with there is no way to tell. The tips of the arms do have about .5mm wear from interference with the bearing.

Are there other signs I'm missing? Still not clear about what's not working and why.

Thanks,

[3D914]

Did some more research, and found that I did buy my the clutch disk new/used from the guy I bought the engine from. Was intended for a 944 NA, so it should work.

I also recall that I used the flywheel on the used engine with my other parts. Its possible this flywheel was at the end of its life. I checked the offset distance from the base to the top of the mating surface with the disk and measured 5.5mm. However, the heads of the flywheel mounting bolts sit 8.5mm above the same base. That doesn't even make sense.

I also measured the flywheel side of the clutch disk and the center shaft is flush with the mating disk surface - explains the interference. On the back side the disk/spring assy extends over 17mm from the back face of the disk surface.

I checked the OD of the bearing tube and its 33.5mm, while the ID of the bearing is at 34mm - so no issues there.

Anyone know the specs for flywheel and disk that I can measure against?

[AA_Ezra]

Just an idea here, and i will check my recently resurfaced flywheel and tell you the step distance from were the pressure plate rests to were the clutch disk touches the flywheel.

Maybe there is not enough play to let the clutch release?


I did notice that when i installed my new pressure plate that it was firmer and did seam to stand a bit taller compaired to the used one when lying on the bearing and spinning

[Rasta Monsta]

If the fork is touching the bellhousing, you have a geometry problem. Wrong disc, out of spec FW, or out of spec PP.

[3D914]

Even though I can't find any specs on the face offset for the flywheel, a friend checked the offset from my old engine and it was at least 6.5mm. I double checked my current one and its closer to 5mm than 5.5. That will account for some interference.

Once I pick that FW up this weekend I'll see how the disk mates with it.

When it was installed the release lever was moving around 17.5mm and would just touch the forward part of the hole in the housing, which makes sense now.