Kolbjorn S

Got a new-off-the-shelf clutch release bearing last year, then after a few months it turned noisy. Symptoms: with car running and standstill, when depressing the clutch it's quiet, releasing it with gear lever in neutral and there are distinct grinding/rumbling "bearing" noises.
So that release bearing got changed under parts-warranty a month back; and a week ago the noises came back! So now I'm wondering what can cause new release bearings (or at least I presume it is..) to become so noisy so qiuckly? Perhaps "Monday morning" production runs, or somthing else...?

Peter F

I can imagine a couple of potential reasons.
Worn pressure plate fingers, wrong clutch arm or worn clutch arm bushing.
Not sure if the guide tube would cause something like this?
Did you replace that with the T/O bearing?
I have just completed changing the Pilot bearing, T/O bearing, Guide tube, Clutch arm and arm bushing.
Had exactly the same symptoms like you describe.
Cross my fingers it will be OK now, PO had replaced the clutch disc but not the rest.

Cheers/Peter

worf928

I agree with Peter. The simplest explanation is that the t/o bearing is not matched to the required (and updated) release arm lever and guide sleeve.

Mongo

my dad's '85 928S had a similar incident. However, the throw-bearing welded itself to the pressure plate

Dave Howerdel

I always replace the following and consider it to be cheap insurance:
clutch discs
pressure plate
pilot bearing
t/o bearing
release arm bushing
guide tube

I coat the intermediate shaft with a light amount of moly grease and surfaces are checked for trueness. Then a light going over with emery cloth or similiar in a cross hatch pattern.

Done 4 clutches this way and all still perform flawlessly.

Failure in such a short period of time sounds like mismatched parts to me as well.

worf928

I've been into 4 '87+ clutches as well.(So, I'm an expert... NOT ) Based upon this very small sample set I've drawn a tentative conclusion that the failure order of the parts is:

- release arm bushing
- pilot bearing
- t/o bearing
- disc
- pressure plate

I did an '87 a few weeks back with 100k+ miles. The disc was at about 2/3-of-new thickness. New pilot bearing, bushing, and some of the Porsche-spec "Olista Long-time EP" grease was all that was needed. Clutch is like butter now.

I have a suspicion that running the clutch with a bad pilot bearing and bushing for too long is what fraggs the t/o bearing and leads to pressure plate deterioration.

As for cheap insurance... that pressure plate is spendy.

Dave Howerdel

I do agree with your order of failure. The release arm bushing is a quick fix and can prevent quite a bit later. I believe it was the ultimate cause of at least one of my t/o bearing failures(over time).

To me my time is more valueable. Having to go back in multiple times costs me alot more, Especially when I am trying to diagnose a problem with tired old parts that "look good".

All of the ones I've done were <87 so were talking <$ 750 for all parts mentioned above. I do realize that the later pressure plates are a good chunk of change!

Kolbjorn S

Thanks guys, I definetely need to educate myself a bit better on this clutch. New parts changed by P-dealer when I bought the car > 1year back were
- clutch disc
- master cylinder
- release bearing
- guide tube
- "grooved ball bearing" whatever that is; possibly pilot bearing?
The pressure plate was re-machined, and the clutch except the noisy bearing works really well.

So it seems I'm missing
- release arm bushing which I assume is the same as clutch arm bushing
- the clutch arm itself
- not sure what pressure plate fingers and release arm lever are?

Peter F

Pressure plate fingers are the center of the pressure plate that the T/O bearing and clutch arm are attached to.(the flexible springs)
These can be worn where the T/O bearing is attached, it might be because the Clutch arm is of the old type or that the bushing is/was worn out.
If this is the case it might cause the T/O bearing to move on the pressure plate, and because of this wear out prematurely.
Just guessing and only way of telling is to open it up and make sure.
The later clutch arm that should be used with the new type of T/O bearing has part number:928 116 832 09 older type is 928 116 832 08.
Newer type have slighly different shape where the T/O bearing makes contact and was introduced on the GTS from -92.(flatter shape)

Cheers/Peter

Kolbjorn S

Great, will check it out - if you guys ever visit Oman the 's on me!