Clunk from transmission - any ideas??

[993_C2S]

I recently took my manual 993 C2S into central London. Not a nice experience made a worse by an intermittent clunking noise coming from the transmission. This noise would only appear when the clutch had been depressed for say around 15 seconds at traffic lights - upon releasing the clutch I'd get a clunk. Having the clutch depressed for a shorter period of time didn't cause the problem. Clutch is otherwise operating fine - no slip, judder, and feels progressive and weighted normally. Any ideas what could be causing it?

[rumplestiltskin]

Could the clutch be over-heating a little ?
15 secs to me seems a long time to have a clutch depressed while standing still, I always slip it out of gear.

R.

[993_C2S]

I agree, 15secs is too long, but the with the amount of stop/starts to make I end up leaving it in gear sometimes.
Is this a common occurance on 993s when they get hot?

[SURJ_993C2S]

No its not a common occurance. No idea what your problem may be but I can tell you that I've never experienced it in my 993C2S.

Do you feel anything in the pedal travel when you release the clutch? Where is the 'clunk' at your feet or somewhere along the transmission tunnel?

[993_C2S]

Thanks Surj. The clunk was coming from the engine bay and I did not feel the clunk when letting out the clutch, I would just hear it.
I took the car out yesterday and it didn't do it at all, but then I wasn't in any stop/start traffic where the temps would have built up, or where the clutch would have been put under strain.
I'm only mentioning the clutch as the noise would only appear when the clutch was released after being depressed for a bit longer than usual.
Any suggestions what it could be?

[SURJ_993C2S]

'fraid not. I've never heard of it on any other forum (fwiw) either.

You may want to post up a question on the JZ website. I haven't been there for a while but you used to be able to post technical questions that usually elicited an answer from Steve or Jonas in due time - or give them a call; they're very helpful.

[993_C2S]

Thanks mate, I'll give them a shout.

[james_j]

From the sound you describe, it's almost like it might be the DMF (Dual Mass Flywheel), assuming that's the type you've got (i.e. standard). When they start to get a bit knackered they can make clunking noises, but not necessarily in the scenario you describe - do you also get a clunk when you switch the engine off? (I'm guessing not, otherwise you'd have probably said.)

[993_C2S]

James, I only noticed the clunk on the recent trip into London, and it only appeared when I left the car in gear with the clutch depressed for a longish period of time. Even having it depressed for a short period, but in otherwise identical conditions didn't cause it to happen. No other odd noises at any other times. I guess I'll just have to keep listening out for any changes.