Mark944na86

This evening the S2 left my wife stranded needing a tow home. Drivetrain power loss. Got the car up on stands, and started checking things out. Appears to be a clutch problem: I took the inspection/access plugs out of the transmission bell housing, and checked the driveshaft/transmission coupler for rotation. Problem: Rotation is not being transmitted to the driveshaft from the flywheel.

The clutch hydraulics look OK: I can see the end of the clutch fork move through the expected range when the clutch pedal is depressed/released.

The clutch just does not seem to be engaging. This is where I'm trying to get a picture of what could fail that would lead to that effect. It's like the pressure plate must somehow be jammed "open". The clutch pedal feels reasonably normal, but is perhaps a bit lighter than usual when depressing the clutch pedal. Perhaps because the resistance of the diaphram spring is not being felt, because it isn't actually engaging on the clutch plate? In other words, the diaphram is stuck "open", or in the released position. But what could cause that to happen?

No unusual noises right up until the failure. Even then, no real noise -- more just a silent loss of drivetrain power. Clutch has been strong -- no signs of slipping or shudder (and it was only replaced last year.)

If anyone has seen a failure like this, please chime in!

JohnKoaWood

If I had to venture a guess I would say a spring at the center of the clutch disk broke, and has the pressure plate locked open.. would need to be disassembled to confirm.

Other possible cause could be broken pressure plate, however this is much less likely!

MichelleJD

I had it happen the other way (clutch would not disengage), turned out to be a broken clip on the TO bearing so the fork wasn't moving it. I have no idea how the clutch setup would stay disengaged.

The torque tube (driveshaft) doesn't turn at all?

931guru

Rubber center clutch finally broke through the "limp home" stops.

JohnKoaWood

IIRC the S2 has a spring centered clutch disk from the factory.. not rubber like the earlier N/As... but I could be wrong...

Mark944na86

The S2 has a rubber clutch from factory, but in this case we are dealing with a spring centered clutch. I replaced the original rubber clutch with a standard Sachs spring centered one last year.

Of course, the "normal" failure mode for a clutch is exactly what Michelle says: The clutch won't _disengage_, because the pressure plate is in its natural position due to the action of the diaphram spring, but for some reason (e.g., hydraulics, clutch fork failure) can't be released.

That's why this failure is puzzling. I've though about it, but I can't visualize a failure that leaves the PP released state like this. If there was a broken spring or some other debris between the clutch plate and the PP, you would expect to hear a lot of racket and feel lots of vibration. This just feels like the clutch is mysteriously disengaged (even though I can see the the clutch fork moving normally as the pedal is pressed and released.) Weird.

Anyone know of or recall hearing about a scenario like this one? I'm wondering if there is some way the throwout bearing might become detached from the diaphram, and that would effectively leave the PP without spring pressure? As I say, I can't really visualize exactly how that would work, but thinking out loud here...

PorscheDoc

Exactly. S2 does not have a spring center disc from the factory

edit, just read the reply above.

My guess is the center has sheared from the hub (broke the metal tabs). Very common on the S2 spring center discs. I can post a picture if need be.

Mark944na86

Yikes! I've never heard of this one. Would this be fairly silent? Looks pretty catastrophic!

Sysgen

That would be my guess also, I've seen it happen twice now, on my car and on friends.

PorscheDoc

Yup, it will be a quiet as can be. This disc failed after about 2 years on the track (stock class S2), and the replacement recently the same way on the track after about 3 years of occasional use. Looking for a better replacement for the S2 other than a Sachs disc. First time I questioned abuse, but the 2nd time it was me driving making a smooth 3-4th shift on the straight when it let go.

Mark944na86

Well... yeah! (if this is a common thing.) Any ideas? What would have to be changed over to put in a 951 clutch, for example? (Clutch bell housing at least I know would have to be changed.)

Mark944na86

And what about the Vertex aftermarket clutch disk? It looks a bit beefier than the Sachs, perhaps?

Vertex "Power Friction" aftermarket clutch disk:



Standard Sachs clutch disk:

Eric_Oz_S2

Mark,

Sorry to hear of yet another problem.

You could try the Lindsey Racing Spec 2

http://www.lindseyracing.com/LR/Pors...LR-SPD-31.html

My clutch was replaced by the Porsche Centre about 5 years ago - since then it has had a hard life and still going strong. Not sure what they replaced it with, though it had a Porsche Part number. I would have thought they don't make the rubber centre version anymore?

MichelleJD

Wow - that's nasty!

Chris White

Does your wife like to drag race when you are not in the car??!?

The first thing to check is for fork movement in the bellhousing inspection port – it that is alright you are down to fork or disc failure.

If it is disc failure then make sure you check the torque tube – I have seen bad bearings in the torque tube cause enough deflection that the disc becomes uncentered and then the hub will not last long.