My clutch is acting very peculiar. It used to engage and disengage near the top or middle of the clutch pedal travel, but yesterday after a 2 hour highway drive (read no shifting) my clutch only barely disengages at the bottom of the clutch pedal travel.

I measured the slave cylidner travel and it is 14mm. The specifications I have say that it should be between 15-18mm but it seems very close.

I am not leaking any brake-clutch fluid and my tank is as full as it should be.

What would cause such a sudden change in the clutch? What should I check?

The car is a 75K mile car and the clutch was replaced at arounbd 40K miles already (I don't know what type of clutch was put in, rubber or spring center).

I am perplexed by this very sudden change and I don't think the clutch should be worn out because I have been launching the car gently.
Any help would be greatly appreciated.

 

Your clutch slave cylinder may be shot
or you've got air in the system

 

J Chen,
If the slave is shot, wouldn't the travel of the release rod be less? Also, I haven't touched the clutch system in about 7 months, what would change the air in the system? I properly bled it back in July. Also, if the slave was shot wouldn't it leak fluid? Thanks very much for the reply.

 

Master cyl or the hose between the slave and master.

 

Todd,
I just read your post with a very similar problem. If the hose was bad, wouldnt it leak? Also, is there anything you can do to test if it is the master cylinder? Thanks,

 

Yes, it would probably leak, but it is not always noticable; i.e. it can leak into the firwall and under the carpet, so you would not really notice it.

 

I throw in a couple other failure options. If it was replaced with a spring centered clutch (the one with the 6 little inner springs) you could have thrown one of those and it is getting chewed up. Or the grease on the drive shaft splines gave up the ghost and the disc is not falling free all the way. This would be especially true if the old white Porsche grease was used on replacement or no clean up of old grease and refreshing.

I don't know how you would tell if either of these options are going on without some sort of scope to peer in and explore. You can't just pull of the bellhousing and take a look see in a short amount of time.

 

On my case they are thinkikng it is the clutch fork, either one side has slipped out and/or broken.

 

Todd, that could be possible. If you have ever seen the fork it is sort of thin/small where it grabs the throw out bearing. And the ridge where it grabs the TOB isn't very deep. A really stupid design if you ask me. If the bearing ever started to seize up then it will rub the fork's fingers and who knows where that would lead.

And some people have actually bent the fork.

BTW, that fork ain't cheap, I think it is about $300 USD, IIRC.

 

Iceshark,
Thanks for the other possibilities. I measured my clutch wear in order to ensure that I didn't need a new clutch. I am at 22mm and 18mm is new with 38mm being the time for replacement, so I don't believe that I need a new clutch (unless it is one of the springs).

I believe that one of the cylinders (either master or slave) is not working properly because I have limited travel of the clutch release rod. Would either of the situations you described limit the movement of the clutch release rod?

Thanks for the suggestions,

 

Maciek,

You have the S2 and I'm not as familiar with that. On my 951S the wear limit is 34mm. When I had my clutch problem I was well within that, I'd have to look up exactly where I was at but I was good from the measurement.

But my clutch turned out to be a disaster and had worn down to the rivets. Ground a couple heads off, actually. So much that they and the missing springs ground down my flywheel so bad that it took 0.025" to true up. Normal resurfacings only take 0.005 to 0.010 As I said, it was a disaster.

When you say limited travel of the clutch rod do you mean the slave rod that engages the throw out bearing fork? Then I would suspect something confilcting inside the bellhousing. Thrown spring, the fork, PP, who knows unless you get in there and look.

Usually when the clutch master or slave cylinders go bad they will leak fluid and you will drop the clutch pedal to the floor and it will stay there due to the return spring arangement unless you pull it back up.

 

Dan,
The engine and clutch are from an 86 951, they just happen to be in a S2 cab body...
I am well within the wear limits as well, in fact from the wear indicator, I have a nearly new clutch.

I know that the cylinders typically leak, but I really don't know what else it could be (unless it is the scenario you're describing)

The slave rod does engage the throw out bearing (I think, I'm not certain if I understand the mechanics), I can still shift fine and the clutch completely disengages, its just my friction point is very near the floor and it used to be much higher on the pedal travel. Also, when I measure the travel of the slave rod, it is about 13.5mm and the specs say the minimum travel is 15mm.

How do I go about ensuring that it is not a spring or something else without removing the bellhousing? Is there any way to look in?

I have a new tranny to install, so I could do the clutch at the same time, I just have to come home from school to work on the car, so its always on a weekend. I would hate to come home to do the tranny and realize I needed a new clutch and have to wait another week for the clutch to get here.

Thanks for all the info!

 

To clarify, I don't if something is limiting the travel of the slave rod or if there isn't enough "push" from the cylinders. I'm going to check if the inside of the firewall is wet...

 

If you can completely disengage the clutch then I think you are fine on the clutch internals. No creep forward with clutch pushed in in first gear. No hard shifts. Right?

Must be something in the cylinders, lines, the clutch pedal adjustment rod, or firewall. While it seems hard to believe, there are reports of guys having the firewall fracture around the master cylinder. So then you have enough flex that the clutch pedal doesn't have a firm base to push on. Get a helper and look for that.

Then it must be somewhere in the hydraulic system. There are lots of places to leak or get air in.

Finally, to tell you how it works since you've never seen the inside of the bellhousing. Hans and Franz really designed this clutch as a bunch of parts just waiting to fail. The fork pivots on a shaft and grabs the throw out bearing by a little ridge in the bearing. That *pulls* it (not push) and the pressure plate fingers back and releases the pressure between the PP, disc, and flywheel. Now the drive shaft is free.

But the TOB is held into the PP by a snap ring and that snap ring is on the inside of the PP fingers so you are pulling on that ring rather than a substantial solid chunk of TOB. And you are pulling rather than pushing. The clutch fork fingers are thin, IMHO, as is the ridge on the TOB they grab to pull. Failure spots everywhere.