[Mgs] Clutch problems.

[PaulHunt73]

You say 'obviously not working', what do you mean?  Not engaging?  Not 
disengaging?  Or something else?

You say the hydraulics seem fine and the pedal feels OK.  Therefore there 
must be back-pressure from the cover-plate diaphragm springs i.e. from the 
slave piston via the slave push-rod, release arm and release bearing to the 
cover-plate, or the pedal would feel ridiculously light with just the pedal 
return spring acting on the pedal.  Without that back-pressure after two or 
three pumps the slave piston and fluid would have been pushed out of the 
slave cylinder, as it's only the cover plate that pushes it back when you 
release the pedal.  Therefore the release bearing must be in it's correct 
position, even if the retaining springs hadn't been fitted.  If they hadn't, 
unless the gearbox was standing on end and the engine lowered down onto it, 
I very much doubt the release bearing would have stayed attached to the 
release arm, and there would be no back-pressure from the cover-plate to the 
pedal.

If the friction plate is put in backwards you have a gap between the 
friction surface and the flywheel which is more than the thickness of the 
friction plate, and the cover plate is held that much further away as well. 
Even if that can be bolted up to the flywheel it will push the diaphragm 
springs, release bearing and everything else further backwards by the same 
amount.  Given the mechanical advantage of the release arm the slave 
push-rod and piston will be pushed into the slave cylinder by several times 
more than the normal travel of the piston, which will bottom the piston in 
its cylinder.  If, with the pedal released, you can push the piston further 
back into the cylinder, and get some free-play in the linkage, then it is 
very unlikely that the friction plate is the wrong way round.

If the spigot bearing is too small then someone would have had huge problems 
getting engine and gearbox back together.

I agree that it has to come out again, but I'd do what whatever is needed to 
make the unusual noise and hope it leaves some witness marks that are 
visible when you dismantle things again.  It could be that the release arm 
and hence the release bearing is not aligned correctly and so the release 
bearing casting is rubbing on the cover-plate boss that the carbon surface 
rubs against.  I assume this is a carbon bearing and not a roller?  If a 
roller that has to be the main suspect for any unusual noises that occur as 
you apply pressure.  If the noise only occurs towards the end of the pedal 
travel that I'd say it is something like release arm or release baring 
rubbing on the cover plate.

This assumes that the correct clutch kit was fitted, and there is nothing 
wrong with it.  My son has recently had a clutch replaced on an M5 and the 
fitter went through three different ones fitted five times before he 
discovered that despite the correct numbers on the boxes there was a defect 
on the whole batch causing then not to disengage as they should.

PaulH.


----- Original Message ----- 
> Have a rubber bumper B with clutch problems.  Hydraulics seem fine, pedal 
> feels okay, not
> great, the slave moves the lever enough that it should work.  But with the 
> engine running
> when you push in the clutch pedal there is an odd sort of grumbling noise 
> from the clutch,
> and it is obviously not working.