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MG Midget and Sprite Technical - Grinding clutch

It's done 5,000 miles on totally new clutch until yesterday. Stopped at lights then really difficult to engage gear, then few hundred metres it became impossible to engage a gear at all.
Grinding noise when clutch pedal depressed and engine stalls at tickover. Plenty of fluid in master cylinder, good pressure when pedal depressed - so suspect slave is ok. Gear selection fine when engine switched off. My suspicion is its the carbon thrust washer - what do you think?
Invested a while ago in a Peter May roller bearing thrust release so that'll be fitted if the engine needs to come out, do you think it's worth investing (on a sale or return) in a complete clutch set, just in case?
It's my daily driver and back to work this morning after two weeks off - great timing, I think the gremlins have been at work again!
Jeremy 3

Sounds like the carbon is gone indeed. If clutch plates are ok, just replace the bearing. You have to alter the pressure plate although, grind the metal bearing surface off.
Maybe it's a good idea to replace the fork bushing, I now I should have.... :(

Alex"can't wait for parts..."Matla
Alex G Matla

Release bearing at 5K miles? Should last >50K.

Think also re spigot bush breaking up...

Anthony Cutler


I presume this is an A series engine with carbon release bearing. Hopefully you're aware that you should never ride the clutch or you can wear them out very quickly, if you don't then as Anthony says they should last much longer. Maybe on of the modern poor repro release bearings giving up early?.
David Billington

I'm with David B on this; I fear there are some dodgy thrust carbon bushes out there!
David Cox

Maybe the fork-bushing is badly worn, causing the bearing to run excentric in relation to the pressure plate...
Alex G Matla


Because of the design of the A series clutch release mechanism the carbon release bearing will always run eccentric at some part of its motion, bearing wear can make the situation worse. This is one reason why roller release bearings are not ideal when fitted to the standard arrangement, they do work for some people and it seems are not so good for others. I knew a guy years ago that made his own with apparent success.
David Billington

We had a batch of rubbish release come through. Easily identified by the yse of a roll pin through the side of the cast iron casing into the carbon. Presumably to stop the carbon from spinning because there isn't enough interferance fit. It causes it to shatter from there.

If that's what you have, take it back and ask for your money back, along with the labour cost of fixing it. Don't take "we haven't had that problm before" crap, people in the trade know about the problem but despite having settled a number of claims they have stock they want to get rid of and try the deny-all-liability approach.
We didn't. As othrs have notd, they should last much much longer so after we discovered the problem we paid out on the first claim and dumped the rest. And have been very particular about the type of release bearings we accept ever since.

If it is the bearing, check the matching release ring on the diaphragm spring - it may have been damaged.

We had a roller release bearing on one of our cars when we bought it, but changed it after two failures (the last being on the steep east ramp of the Stelvio Pass which nearly caused a divorce as I didn't want to believe Bron when she radioed that she couldn't get it into gear ...)
Paul Walbran

Thanks for all the helpful ideas and suggestions - hadn't thought about the fork & bearing which was the only part not replaced.Thanks Alex.
I'll check when the engine & gearbox come out to see if it's a dodgy bearing as I don't ride the clutch and if it is, it's going back where it came from, thanks Paul. The original managed to last for 85,000 miles and was replaced only because I thought it best to do so with a new clutch! Did replace the spigot bearing so hope that should be ok - we'll see.
From what you've said I take it the jury is out on the roller release bearings?
Thanks again.
Jeremy 3

I tried a Moggie roller release bearing, and it was too heavy. It nodded against the rotating thrust plate and moved gradually backwards, so that it had to be pumped back up into contact again every time I wanted to use the clutch. At least, this was Tarquin's theory, and it made sense to me.

And it was a bloody long way home!

Probably Peter May's units are lighter, or better balanced.

Nick accurately described the reason for our near divorce!
Paul Walbran


was your roller release bearing from Peter May as I'm tempted to use it if it turns out to be the carbon bearing which has failed?
Good to see you're still married though!
Jeremy 3

Unfortunately I can't help there - we inherited it when we bought the car, so I don't know its origin.
Paul Walbran

Thanks Paul anyway. All will be revealed at the weekend - fun eh.

Jeremy 3

Here'a a photo of the culprit!
Note the complete absence of any carbon - it was sprayed all over the bellhousing instead.
It's been replaced by a similar item from MGB Hive which is made in England so let's see how long this one lasts.


Jeremy 3

Ha, I have one of those too !
Alex G Matla

Me too!


So it was as suspected, quite a common occurence when clutches get to the end of their life - the remaining question now is why it failed after relatively little mileage. There is not enough left to determine whether the "roll pin" problem I experienced was the cause, but I would suggest that when buying replacement thrusts or complete kits make sure it hasn't got one.
Paul Walbran

Thanks Paul that was the first thing I checked and it didn't have the pin you mention.
I'd forgotten just what a pig bleeding the clutch slave cylinder is as everything else went together (reasonably) ok.
Let's see what the next problem is!

Jeremy 3

This thread was discussed between 14/09/2009 and 28/09/2009

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