Subject: Re: [Mgs] Clutch problems.

From: Barney Gaylord <[email-masked]>
Date: Tue, 19 Nov 2013 00:06:39 -0600

If the friction disc is installed backward, the center hub with 
springs will foul on the flywheel bolts, and the clurch will not release.

If a new spigot bearing was installed, and the ID is a smidge too 
small, it will bind on the gearbox input shaft.  In this case the 
clutch does release, but the input shaft keeps spinning same as if 
the clutch didn't release.

In any case. if the slave cyliner pushrod and release arm moves at 
least 1/2", and it still doesn't release, the engine has to come out 
to fix the clutch.

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com

At 10:56 PM 11/18/2013 -0700, Mark J Bradakis wrote:
>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.
>
>One possibilty I thought of after I left my friend's shop was 
>involves the throwout bearing.  I didn't install this clutch, so I 
>don't know if the retaining clips that hold the bearing to the fork 
>were new, used or properly installed.  Have any of you had one of 
>these clips fail, allowing the bearing to fall out of the yoke?  I'm 
>wondering if that is a possibility.
>
>Another possibility is the person who did the job put the disk in 
>backwards.  But whatever the problem, the gearbox has to be 
>pulled.  I might get a bit dirty down at Bailey's tomorrow.
>....
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From: "PaulHunt73" <[email-masked]>
Date: Tue, 19 Nov 2013 08:47:34 -0000

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.

[email-masked]

---

From: Jim Juhas <[email-masked]>
Date: Tue, 19 Nov 2013 10:22:41 -0500

I don't know if your car uses a roller bearing or carbon bearing, nor 
did you say that this had been operating correctly and that this is now 
a failure.

If this is a recent failure, I would suspect the throwout bearing.  I 
had a carbon-type one fail abruptly, caused grumbling sounds, and then 
the clutch could not be disengaged.  The carbon had disintegrated and 
fell out of the shell.  The steel/iron remainder of the bearing against 
the pressure plate accounted for the noises.

I have had roller-bearing throwout bearings fail on 60's-era Chevelles, 
and they would make a lot of noise before their failure. The carbon-type 
failure was abrupt, a snap, no disengagement, and noise when the pedal 
was depressed.

On 11/19/2013 12:56 AM, Mark J Bradakis wrote:
> 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,
> One possibilty I thought of after I left my friend's shop was involves 
> the throwout bearing.
> I didn't install this clutch, so I don't know if the retaining clips 
> that hold the bearing to
> the fork were new, used or properly installed.  Have any of you had 
> one of these clips
> fail, allowing the bearing to fall out of the yoke?  I'm wondering if 
> that is a possibility.
>
> backwards.  But whatever
> the problem, the gearbox has to be pulled.  I might get a bit dirty 
> down at Bailey's tomorrow.
>
> mjb.
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From: "PaulHunt73" <[email-masked]>
Date: Tue, 19 Nov 2013 15:43:13 -0000

Had that too.  Gradually making more noise but still working, until it 
suddenly failed.  Then the clutch pedal was very light, and a couple of 
pumps pushed the piston out of the cylinder (no back-pressure from the 
clutch to push it back or weight the pedal).

PaulH.

----- Original Message ----- 
> ... The carbon-type failure was abrupt, a snap, no disengagement, and 
> noise when the pedal was depressed.

[email-masked]

---

From: Mark J Bradakis <[email-masked]>
Date: Tue, 19 Nov 2013 17:33:53 -0700

Wish I had thought to take my camera.  The retaining clips were fine.  
The clutch disk had
not been installed backwards.  But the throwout bearing - or I should 
say the remains of
the throwout bearing were a sight to see.

mjb.

[email-masked]

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From: "PaulHunt73" <[email-masked]>
Date: Wed, 20 Nov 2013 08:19:20 -0000

How old was the bearing?  For a while they were attaching the carbon ring to 
the casting with a roll-pin, but expansion and contraction caused the carbon 
to break up in short order:
http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/rbearing3.jpg
http://www.paulhunt73.webspace.virginmedia.com/mgb-stuff/images/rbearing4.jpg, 
this had done 8k.  The manufacturers soon went back to bonded, but that left 
a stock of pinned floating around, so it's been a case of buyer beware ever 
since.

PaulH.

----- Original Message ----- 
> ...  But the throwout bearing - or I should say the remains of

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