apanossi

Can't figure out what this noise is from my 2002 996. I have been having trouble with a clutch issue involving this noise from the bell housing area. I have posted here before about this but all previous suggestions have been tried without success. I am attaching an audio recording of the noise, which comes on after the car warms up and is idling in neutral, and goes away when the clutch is depressed. This has been a frustrating process since I have so far spent more than $5000 on trying to fix this issue.

The car runs great, but ignoring the noise in the past eventually led to a clutch failure. I have had the clutch kit, flywheel, and throwout bearings fixed about 3 times each by both the dealer and a well-reputed indy. Could this be an issue with the slave cylinder for the clutch? None of this is making any sense.

logray

Could the release lever be involved somehow. Maybe bent?

Do you only hear it at idle or is it present at other RPMs. I would guess so.

It might be worth bleeding and then if no success perhaps replacing the slave cylinder, maybe it isn't fully retracting when you release the clutch?

Not sure of your MY but you can get a new slave cylinder for about $110 + shipping.

And then bleeding is fairly straight forward, there is a DIY on renntech and pedrosgarage on bleeding brakes an slave cylinder.

apanossi

I can only hear it at idle. I'm assuming the noise is still there while coasting in neutral but it's difficult to hear over the road noise. Also, I can't be sure if the noise is there when in gear, again because of the engine noise overtaking it. But I guess it could be there while in gear.

I recently had some body work done on the car and changed out the flywheel again. The mechanic said he would change out the slave cylinder as well, but now that I'm checking my invoice, it doesn't look like it was itemized. I may have to give him a call to see if that was done. Also, I asked my indy about the slave cylinder and he said that it was not related to this problem. I'm willing to entertain that possibility again.

function12

Throw out bearing and or bent finger on pressure plate. My guesses.

logray

It sounds like he had those replaced 3 times already???

speed rII

Gearbox mainshaft bearing? I think that I have read about others that had bearings go bad on the transmission.

997_rich

Really sounds like something going on with the flywheel or trans input shaft (those are at rest when you step on the clutch). It could be also something with the pressure plate cover.

Could it be that one of the bolts holding the pressure plate too flywheel is too long and scraping on the bell housing or engine case? Sometimes when assembling the clutch I'll use extra long bolts to draw the assembly together and trade them out for the stock bolts when fully assembled. or one of the bolts could be backed out a bit and scraping.

Does it make this noise when you're driving?

997_rich

I don't think it's the slave or throwout assembly because when you're putting the force on them (when the pedal is depressed) them they're silent.

997_rich

when they pulled this apart were there any scrape marks on the bell housing or under the flywheel on the engine case? maybe some of the bolts on the IMS are backed out and scraping on the backside of the flywheel? When you're making noise like this there's going to be some scraping/wear somewhere.

what about the old parts (removed broken) can we see some pics? if they're trashed they will certainly show clues as to what's going on. Please don't tell me the shop threw them out.

apanossi

Thanks for all the great suggestions thus far. And yes, virtually all elements of the clutch kit, flywheel, bearings, etc. have been replaced at least 3 times each. Everytime, the noise kept coming back. I'm attaching a photo of my clutch plate when it failed over a year ago. The central shaft splines are completely sheared off. My indy said that there appeared to be nothing wrong with the transmission itself. He also looked at the flywheel and throwout bearings at that time and noted that everything else looked good with normal tolerances on the flywheel.

After searching extensively in the forums, I came across a post that noted a "ticking clutch pedal" and described the phenomenon just like my issue. However, he didn't mention noise in the bell housing area. After replacing all other elements of the clutch system (including slave cylinder), he still had the noise. That is, until he changed out the master clutch cylinder.

Could that be? That a faulty master clutch cylinder is the culprit? How would it fit this scenario?

As an additional piece of information...I can sometimes make the noise go away if I play with the clutch pedal.

apanossi

Here's a picture of my flywheel that was replaced this last July.

Byprodriver

Wow that does not sound good. I recommend you talk to Tony Callas @ Callas Rennsport in Torrance CA & get him to listen to your video. He writes the tech articles for Excellance magazine & PCA newsletter. I'm guessing transmission related cause. It is worth the effort to have flywheel & pressure plate balanced for everyone & especially you.

apanossi

Thanks for the referral. I take my car in to Johnson's Alignment for brake and alignment issues. I used to see Callas Rennsport in the same strip mall, but didn't know anything about the shop or Tony. I will have to take my car to him for a listen.

Macster

Hard to believe that the same hardware was replaced 3 times absent any clear indication it needed replacing. I wonder if someone's not stringing you along?

You say the car runs great.

Just to be sure there is no issue starting the car moving from a stop? The clutch engages smoothly, with no grabbing, no noises?

With the engine idling and the clutch depressed you can select any gear without any difficultly?

Once underway with the engine/drivetrain up to temp hard acceleration in gear does not produce any signs of clutch slippage?

And shifting once underway is without any drama?

If you can answer "Yes" to all of the above, then I can't see how the clutch hydraulics or clutch linkage can be the problem.

Now it may be the linkage is not routed right and a part of it is making contact with the body or an exhaust or bellhousing. Something. Has anyone been under the car when this noise is present to view the various clutch and shifter linkages for any signs of movement?

Have the engine and transmission mounts been checked?

For the clutch's splines to go away like that could be explained by a bad heat treatment of the clutch splines. They were left 'soft' and could not take the load. They want to be quite tough, tough like a gear. In this case a manufacturing defect is to blame.

Or there was excessive drag as the clutch moved from engaged to disengaged which wore the splines down until they could no longer hold. This suggests a mechanical problem. For instance, a misaligned transmssion (or engine) could account for this. But I can't imagine how the transmission and its input shaft and bearings could long stand this without signs of trouble. Well, maybe the noise is the sign of trouble.

The above is why I asked about the engine and transmission mounts.

Absent a clear sign something needs to be replaced and I am not sure there is a clear sign, I can't believe replacing the clutch slave cylinder called for?

For me, at this point if that were my car, I'd want to be under the car with the engine running, idling and someone in the driver's seat and able to work the clutch and shifter and see the clutch hardware move, watch if the engine or transmission moved about.

What I saw, or didn't see, would help me decide what to do next.

Sincerely,

Macster.

apanossi

Macster,
Those are terrific questions and suggestions. The answer to all of your first set of questions is "yes". There does not appear to be any slippage or difficulty in shifting. All gears are smoothly engaged, no stickiness. The car takes off great.

The only thing I personally have not done is get under the car while idling. But I would have to think that my indy already did that and did not find an external problem with the linkages. The Porsche dealer that originally tried to fix this problem definitely did do this and reported no problems. Engine and transmission mounts all look good, and the main transmission crankshaft is centric with no evidence of wobbling, catching, or bend.

I had the noise going on for about 1 year until the clutch failed and the splines were found to be sheared. We (meaning indy) chalked it up to bad manufacturing but of course, Porsche did not see it that way. I'm wondering with the ongoing noise (whatever the source) for that long eventually wore down the splines???

I think my next move will be to swap out the master clutch cylinder, since this is the only item that has not been addressed. I can't give you a reason why this would work or not, but I'm desperate to get this fixed before I get stranded again.