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MG MGB Technical - Faulty Release Bearing

I've checked the archives and can't seem to find anything on it. After about 1500 miles my new release bearing is toast. Pulling back the boot on the release fork a bunch of carbon chunks fell out and closer inspection revealed no carbon bearing surface. Bad noises (grinding and strong vibation in pedal when clutch pedal depressed) began almost immediately after completing a clutch replacement (full deal: pressure plate, clutch disk, carbon release bearing, spigot bush and fork bush.) Failing any bad batches of parts out there, is there any pitfall to my clutch installation that could lead to early throwout bearing failure? PS I don't ride the clutch and even if I did it ought to last longer than that.


Dan deCamp

Dan - Are you by chance installing a heavy duty clutch? If so, that is what is eating your throwout bearing. Moss offer (or did) a standard and a heavy duty clutch and when I first replaced the clutch in our MGB, my thinking went along the line that if a standard clutch is good, a heavy duty must be better. After going through a couple of throw out bearings in short order and having to deal with a very heavy clutch pedal, the penny finally dropped and I installed a standard clutch and have had no further problems with the bearing. Cheers - Dave
David DuBois

Dan. In the past, the "clutch kits" came with a clutch plate (driven plate) and a pressure plate in one box and a separate box containing a throw out bearing. A few years back, the "Borg and Beck" brand name was bought out by another company. I purchased three of the new model clutch kits (one for immediate use, one for a projected engine rebuild and one for my "spares locker"). All three had the throw out bearing packed in with the other two parts with no padding to protect it. On examination, two of the three throw out bearings showed damage due to this form of packing. I contacted the supplier who made a survey of his inventory. He sent me two new throw out bearings and mentioned that about 75% of his inventory showed damaged throw out bearings when packed with all the parts together.

More information would be of use to us. Did you, as I had, receive all the parts in a single box? Did you carefully examine the throwout bearing for chips and cracks before installing it?

We just "stabbed" a rebuilt engine into my 68GT last weekend. Two friends, professional MG mechanics, helped me with this. Two things they found, that I might not have noticed.

First, the clutch fork was worn, after 40 years of use, in the areas that the arms of the throwout bearing seat in. This allowed the bearing, when pressed against the pressure plate, to move, damaging the bearing.

Second, the currently supplied "keepers/security devices" which hold the bearing onto the clutch fork were both poorly made and of inferior materials. They had slid around the bearing and were no longer effectively holding the bearing into the clutch fork.

We installed a new bearing, and other clutch parts, making sure that the new retaining pieces for the throwout bearing were reshaped to provide a more secure retention than they did in their original configuration.

Some of these things may have an implication on your problem.

Les Bengtson

""Borg and Beck" brand name was bought out by another company"

Oh dear, it was Borg and Beck that were supposed to be the best, compared to the Q&H alternative. Are both rubbish now?
Paul Hunt 2

Is it to do with the way your driving?
a lot of people now are driving the mgb like they do there normal cars like holding car on the clutch and dipping the clutch at traffic lights which is burning out the bearings.
some people are getting less than a thousand miles out of the bearings before there toast.
when you install a new one dont hold it on the clutch and take it out of gear a lights

Nobody reads anymore.

STE, in Dan's first post he states:

"PS I don't ride the clutch and even if I did it ought to last longer than that"

Dan, have you pulled the engine yet to inspect the damage? Since it started grinding and shaking almost right away after installation, I would first suspect some sort of installation error. I'm actually surprised that you drove it for 1500 miles like that. Maybe a retaining clip popped off, as someone suggested, though it's certainly possible that it was a bad part and the carbon surface disintegrated at first contact. In any case, it's all speculation until you inspect the part.
Mark J Michalak

Yes i do read the threads and just because he states he doesnt doesnt always mean he isnt.
Ive had over 8 to 10 back last year saying they dont last and most of them didnt realise they were doing it.
The other thing that is happening is the carbon is falling apart due to the way the carbon is put in the carrier.
It is put in with a pin which when hot expands and cracks the carbon bearing thus shattering into pieces.
The uk dont do the roller bearing version now but if you can get one i would go that direction

I'll ask the same question as STE but using punctuation. I've heard that in the UK there is a roller bearing replacement. Is that available in the US? Does anybody have the part number?
1974 mgb roadster
Kenneth Thompson

RE: roller style throwout bearings. Don't know if anyone still sells them, because many people have had problems with them. There's a lot in the archives about it. You have to fit a return spring to the clutch fork, and even after that they still fail prematurely. Mine did and no I DON'T RIDE THE CLUTCH. After that I went back to carbon, no problems at all.
Mark J Michalak

whats the difference between my punctuation and yours,
both have the full stop in the same place,just yours is in a line and mines on the next line?
We have had the roller bearings in for over 12 years and no problems.
Ive heard of people warping their clutch plates trying to getit on to the splines at a funny angle especially when done inthe car.
On the roller bearings YOU CAN RIDE THE CLUTCH!
Other one people do without noticing is resting their foot on the clutch pedal while they drive.
MARK you are not DAN are you, so why do you keep going on about how YOU drive(your not having the problems are you)
Ste Brown

Many years ago I bought a clutch kit from the MGOC and paid extra for a roller bearing release bearing even though a carbon bearing was part of the kit. Shortly after fitting it developed a squeak just as it was taking up the pressure, and about the same time I read about American pull-off kits. I spoke to the MGOC and I suppose unsurprisingly they hadn't heard of problems with the bearing nor about the pull-off kit. Fortunately there have been no further problems with the bearing or clutch, although it still squeaks. Then I asked myself would I be leaving that old bearing there the next time I replaced the clutch? And of course the answer was 'no' so it was a complete waste of money. The Sherpa van and MGB V8 use roller bearings as standard, and the V8 at least certainly doesn't have a pull-off spring, I've done 75k in my V8 so far with the clutch and bearing my V8 came to me with. The V8 part is GRB224, although the midget 1500 part GRB207 is reputed to fit. I can't find a reference to one for a 4-cylinder MGB, the take-up was probably so small they died. Dan's experience could be a one-off, a bad batch, or cheap manufacture. I'd replace with a quality carbon (or least a carbon from a quality supplier) rather than fit a roller bearing.
Paul Hunt 2

There is a batch of faulty release bearings that are made in India. Moss is aware of it. The graphite turns to dust in a few thousand miles. It is a faulty part, not a faulty driver.


Thanks, for your quick responses. I was away on a trip and just got back.

Dave - I did not order a HD clutch but for all I know it may have been one. I did not notice any increase in pedal pressure over what I'm used to. When I pull it apart and inspect I'll be sure to check that possibility.

Les - Yes it did come with a release bearing packaged with the disk and pressure plate. The bearing was packaged though with a plastic bit which covered the carbon bearing surface. No I did not inspect it closely for damage and was unaware that small nicks or dings would result in early failure. I will also be much more careful assembling the tranny/motor to avoid any damage to it as it goes together since that seemed to be somewhat of a clumsy brute force activity. I will also inspect the fork. I do remember the bearing would not fit into the fork and I had to work the pins on the bearing over with emery paper to get then to fit.

STE - I had a Sprite and I rode the clutch mercilessly on that. 50,000 miles later I still had gobs of clutch plate and bearing left. I'm surprised to hear you can kill one that soon on the B. You can bet I'll be really careful now.

Mark - Yeah, I know but I just couldn't bear yanking the engine again. I did poke around, peering through the fork hole early on and the bearing looked fine so I decided to press on. What I really feared was yanking the thing apart and not finding anything...Pearing through the fork hole you can clearly see there is absoloutely no carbon surface left proud of the casting it sits in.

wbacall - Thanks, thats what I was really hoping to hear. Can't remeber if I got it from Moss or my local parts guy but I'll check the reciepts and let the responsible party know.


Dan deCamp

This thread was discussed between 04/04/2008 and 07/04/2008

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