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Whiffy clutch

cobalt911

Well-known member
Joined
9 Sep 2007
Messages
246
Had this latest 993 about 4 months but it had a new clutch a year ago. If I give it the beans off the line I get a lovely blast of clutch stink. There is no slipping or 'clutch issues' but I have never had that smell before enter the cabin (well only once on a previous car but I was definitely slipping it that day) :evil:

Just wondering if that smell is indicative of a new clutch (I doubt it) or something up with the cabin air supply that is drawing it in. Anyway, if anyone out there has had similar did you locate the problem?

Cheers...
 
The best way to check to see if there is a serious issue with the clutch is to put the car in a high gear and give it the beans at maximum torque, probably around 4krpm(If I'm far off GT4 will be along shortly to correct me). This puts maximum load on the clutch in terms of the torque it can transfer. If it copes fine with that you are more looking at the clutch slipping a lot in lower gears due to poor technique or an issue other than the clutch itself.

MC
 
Surprised if you get anything noticeable smell wise if you can't detect slip from the clutch. As before give it a mechanically unsympathetic start and you'll soon find out!
 
You could have glazed it (and now it slips at max torque even though clutch is fully depressed).

I am assuming your biting point-to-floor distance is at least 4" of release arc?

If it is glazed this is just where the clutch plates have been worn (by gentle clutch slip) to a shiny, smooth surface (looks shiny and smooth like a glazed plate). A few aggressive clutch burns (or less gentle general use) removes this glossy surface, restores a roughened surface and gives back some bite.

I used to have to regularly de-glaze a Golf GTI PD150 chipped to within a hairs-breadth of the clutch spec.

It would need the 100% new friction surface to get any consistent clutch grip. However, over quite a short period of time, it would wear smoother (perhaps only a few percent), but then it was a viscious circle. As less friction lead to more slip, lead to more smoothing, lead to more slip etc etc.

I would hold it fully on the handbrake and rev the engine, then slowly let out the clutch until it made a nice smell, then the clutch was back to new again!

Clutch test as per MC, but I prefer full throttle at idle in 4th or 5th (ie go WOT from 30mphish cruise).

The reason is although the torque is higher at higher rpm, the velocity differential is less (and the speed legal!).

ie 1,000 rpm to 1,200rpm is a 20% slip
4,000 rpm requires true 5,000rpm to show same slip.

The 993 has decent low down torque (and the torque/velocity ratio is still proportionally higher than the reduction in torque near idle).

You could also do a stationary (hand-brake on) stall test, again in high gear 5th/6th.
 
Long shot - but is your clutch vent tube properly connected?
 
+1

A bell housing without adequate dust extraction will act like a glazed clutch (the clutch dust is almost as good a "lubricant" as graphite dust)

Should be attached to the air box (rubber tube in large red circle):

s25_1.jpg


snorkel.jpg
 
Mine's exactly the same. New clutch fitted just over a year ago and the problem's been there ever since, it's got better over the last year but it still does it if you botch the pull away or do a quick pull away, not noticeable on normal pull aways. The clutch is soft, smooth and doesn't slip, so the problem is only experienced when moving away from rest. The smell is horrible, a polite description is rotten cabbage!!!
 
Stupid pedals sprouting from the floor?
 
GT4 said:
I am assuming your biting point-to-floor distance is at least 4" of release arc?

WTF :dont know: I'm just getting used to this third pedal lark. Actually it's quite light and bites around halfway off the shagpile :oops:
 
Ha ha, I love you guys. No matter what crappy place in the world I am working in I can get some good 911 banter with you. HELP! HELP!
 
I had that clutch smell for about 6 mths (about 2k miles) following its replacement in my previous 993, but only when in reverse.
 
Many thanks all for the replies (GT4, pics very helpful!).

Tried handbrake test - no slippage
20-30mph in 5th and full beans was fine
The breather pipe is all connected and fine...

So, I think it looks like the clutch is ok but could be the 'glaze' or just 'one of those things'....

Thanks again chaps :)
 

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