Re: E46: Clutch + Pressure Plate + Flywheel = $1500.00

["John A. Virnig" <john@xxxxxxxxxxxxxxx>]

Andrew waffles endlessly...
>...Is it possible that 2 incidents of smoking the clutch might have caused
the
>hotspotting? Does anyone really care if the spots are there or not. I mean,
>do those spots change the performance of the friction surfaces?
>
>And what about the soft-engage mechanism going to pot? Nobody seems to >be
>able to tell me what might cause this to go bad, except to say that "abuse
>would do it."

Andrew -

You description of the failed parts all point to one factor - overheated
clutch.

I'm not going to speculate how the damage was done (that's up to you and
your conscious...or some pimply faced lot attendant) but I can pretty much
assure you that at some point your clutch was baked well beyond what it was
engineered for.  Let me explain.

Two thinks I know about clutches is that they are inherently abused and heat
is very, very hard on them.  You're talking about balanced, machined and
carefully engineered pieces of metal and when you heat metal, you change
it's properties.  Under normal conditions, the metal surfaces of the clutch
will not approach a temperature where damage is likely, but abuse often
overheats the metal bits.  This is why your mechanic offers "abuse" as the
reason things are failing.  Overheating the metal surfaces will cause them
to weaken and warp (same principal as overheating and warping your rotors).
Excessive heat will also weaken spring steel, explaining why the springs in
the soft-engage system and pressure plate were damaged.

Can you overheat the clutch with normal driving?  Yes, I would imagine so.
But it's not likely.  Holding the car on a hill will contribute to clutch
wear, but typically will not overheat the clutch unless it's a very steep
hill and it's a very long light.  Ditto slowing down using the clutch.
Overheating is associated with repeated hard launches (smoking the clutch,
as it were), towing something with a vehicle not meant as a towing vehicle
or getting the vehicle stuck and trying to "unstuck" it using the clutch.

Engine mods for more horsepower will also cause a clutch to slip, even when
you just roll on the throttle (got some first hand knowledge about that
one).  If you have, you should consider a competition clutch.

So, while I'm not in any way telling you that you overheated your clutch, I
am telling you that your clutch somehow got overheated.  That it cost you
$1500 sucks regardless, but I gotta side with the dealer on this one.
Sorry.

John Virnig
'97 328is

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