MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Squeaking noise from clutch bearing

Occasionally I get a light squeaking noise when I push the clutch pedal. This usually happens after a reasonably long run, and then a stop for some time. When I then start driving again the noise is often there, but it soon disappears.

The release bearing is the standard coal type, and has been in the clutch for 17.000 miles since 2005. I measured it in 2009 after 10.000 miles when I changed the ring gear on the flywheel. It was then very nearly as thick as the new release bearing I keep as a spare. I do not drive much in town, so I really donīt think it is worn down now.

I have the original 3 main engine in my ī63 MGB, and as you know this engine does not have a proper oil seal at the rear crankshaft bearing. My theory is that some kind of oil mist gets to the release bearing when the engine and clutch housing gets thoroughly hot, and that this causes the squeaks. After a few depressions the oil is burnt of and it is quiet again.

Does this make sense?

Tore
Tore

Coal - I like it :o)

Oil on the clutch usually results in clutch grabbing in my experience, together with oil dripping out of the hole at the bottom of the bell-housing, which should have a split-pin in it to keep it open.

Many years ago I noticed my clutch would make a noise if the pedal was pushed to the floor, and I could feel a vibration through the pedal, so I just didn't push it to the floor. But then it started getting noticeably worse when I was on a run 60 miles from home. I decided I wasn't going to use the clutch unless I really had to, and managed to get all the way home through towns, traffic lights, roundabouts and junctions just using 4th and OD 4th, and even back into the garage! Once safely parked up I pushed and released the pedal, then pushed it again and the release bearing broke! Something had been wrong in the alignment and the metal casting had worn right through.

I stupidly used a roller bearing release bearing with the new clutch, and that started squeaking just as the pedal started to take up or release pressure from the cover plate. I feared failure, but nothing happened. Then many years after I realised it had stopped squeaking, and again feared failure, but again all seems to be well.

So I'd say it's down to exactly when and how the squeaking starts and stops as related to pedal pressure that's important. Did you use the lube that should have come with the clutch kit on the release bearing pins, splines and pilot bearing?
PaulH Solihull

I had the same noise for a while and then permanent howling. I could change gear though. Took the engine and gearbox out thinking it was the release bearing and....it was. No coal left what-so-ever! And there was only a clip on the one side (on the pin holding it to the fork). My graphite relase bearing had disintergrated to nothing. The inside of the bell housing was a dark grey mess.

/Moss (by the way, is there not a town called Moss south of Oslo?)
Moss

Paul,

There is no vibration in the pedal, and I forgot to say in my first post that this sound has come and gone for at least a year. When I had a look at the bearing in 2009 everything looked perfectly aligned and free moving. I only put some grease in the spigot bearing.

Moss,

Yes, 50 km south of Oslo, where I live, there is a town called Moss. Quite a nice place! I hope my bearing will not disintegrate the way you describe. Next week end I am going on a 100 km trip, then I will be at home for a couple of days, and then it is off to MG Live at Silverstone via Denmark. I guess that will be exactly the time I need to change the bearing if needed!

Tore

Tore

Interesting and timely thread. I've been hearing a strange sound, plus feeling a vibration in my pedal when pushing it all the way down, intermittently for over a year now. It seems to happen randomly, and when it happens, I usually can't make it happen again by depressing the clutch pedal all the way down right after. I can only wait until it happens again. That being said, a couple of days ago, it was happening whenever I pressed it to the floor, but would never do it if I didnt push all the way to the floor. Sounds alot like Paul's symptoms. I also have a leaky frost plug in the middle of the side of the block that I can't effectively whack with the engine in situ. Maybe its time to pull the engine and change out the clutch bearing and do the frost plug at the same time...
Erick Vesterback

I've had the same issue on 3 of the 4 BGT's I've owned to a greater or lesser degree. On my current car the symptoms are now much worse although the clutch & bearing were replaced last year at 45,000 miles using a Unipart clutch kit from the original factory unit. For the first eight months following the new clutch kit including a new coal* bearing the clutch worked beautifully and now the problem only occurs once the engine has warmed up well beyond the point where the temperature gauge indicates normal working temperature.

The problem on this car is noticeably worse than previous cars with the noise being clearly audible from outside the car, with my previous B's it was little more than an unpleasant vibration through the pedal.

A few weeks back I chocked the clutch pedal down with a block of wood wedged between the pedal and the seat frame to see if I could identify what was causing the vibration. I found it only took a little sideways pressure on the clutch fork arm for the noise to stop, which would indicate that the vibration is being caused by the release bearing being slightly off-centre. Short of removing the engine and fitting a new release arm and bearing (the car's now on 51,000 miles) I've considered either attempting to lubricate the bearing with graphite lubricant or fitting a small expansion spring between the fork arm and some static point on the car's chassis by way of a 'bodge'. It seems to me this problem is caused by the bearing running slightly off-centre although why this should become more prominent when the car warms up has me wondering.

I've Googled this issue and apparently it occurs on other vehicles with similar throwout carbon bearing/hydraulic setups and fitting a spring either from fork to a static point or across the slave cylinder seems to be a work-around. I've seen an article for the MGB (sorry I forgot to bookmark it) where a short tension spring was fixed with an improvised bracket on the release arm to the bleed nipple on the slave cylinder and I wonder if this would do the trick?

I have considered that this problem may be caused by a smear of grease being left on the release bearing during fitting, hence the delay before the problem becomes apparent and the heat related onset, rather than it being a faulty bearing per se, after all the carbon release bearing was surely never designed to be the most precise mechanism?

I don't want to have to pull the engine just to replace a coal bearing with another coal bearing only for it to show the same symptoms after a few months, so I'd like to apply a reasoned fix, albeit a workaround, before I go down that route.

Thoughts & suggestions?
Mike

Short update: Just went for a little trip, not long enough to get everything thoroughly warm. Clutch is absolutely quiet, no matter how far I push the pedal.

On my car this phenomenon may be related to the temperature and the length of the run, though I am not sure of it. I never feel any vibration in the pedal, just occasionally the squeaking noise I described in my first post.

Tore
Tore

Mike - if you only get the noise/vibration on pushing the pedal the spring you mention is unlikely to do anything, that only pulls the release arm back to a stop to pull the release bearing away from the cover plate, which shouldn't be needed in any event. Don't forget the pivot on the release arm, if that is worn it could still cause the problem with a new release arm and bearing, fortunately mine didn't. It still begs the question of why the release bearing was rubbing on the cover plate enough to wear through and break, when the new one doesn't, when only the bearing and clutch assembly was changed. This happened very soon after getting the car 22 years ago, when I wasn't confident enough to tackle the job myself so I didn't see exactly what things were like inside. I've done one (for someone else) since then.

There was a period when the 'coal' ring was pinned in the casting instead of being bonded as previously, and these are known to shatter in very short order - http://www.mgb-stuff.org.uk/clutchtext.htm#pinned Hopefully you didn't get one of those! There is another case after that where the carbon wore right down and the casting was operating directly on the cover plate, until that disintegrated. See if you can get a finger inside the bell-housing by displacing the rubber boot on the release arm, and see how much carbon there is around the hole.

PaulH Solihull

I too am experiencing a very similar problem on my 68 BGT. After hearing that 'whirring' sound all to often, i pulled off the rubber boot on the bell housing that surrounds the release fork and stuck my finger up in there.(I know, nothing good can come from blindly sticking your finger in a hole...well, in most cases anyway). Sure enough, bits of carbon from the bearing came out. Pulled engine, nothing left of the bearing face, and replaced with same type from Victoria British. BTW...Both clutch and bearing were new less than 4000 miles ago.

Now i have similar 'whirring' sound but only when i'm letting the clutch out with transmission in gear and giving it some gas. If i'm just sit still and depress the clutch with, trans in gear or neutral...no noise. When you under way and driving and shifting i don't detect noise.

Here's the kicker....I now have oil coming out of the hole in the bottom of the bell housing,and ONLY when i shut off the engine, not while its running and parked, just when you kill the engine. And not just a couple of drips, but a puddle.
I do not remember that before i pulled the engine and did the bearing change. surely i would have noticed that amount of oil.

Are the two related?
Is the new bearing faulty?
anyone know of a better product? or are they all aftermarket sub par?

Thanx for any input
DS
Dennis Silance

I've not heard of that symptom with the oil leak before, but it does figure as the crankcase in all but the earliest engines is under slight negative pressure, which should tend to prevent oil leaking from a worn seal with the engine running.

The noise sounds like the friction plate, quite possibly because it is contaminated with oil.

I've always been concious that parting the engine and gearbox for a clutch change is likely to put an unusual stress on the crank and first motion shaft oil seals. Some recommend that you replace those as a matter of course when doing the clutch, also replace the pilot bearing, but personally I think there is as much chance of putting faulty components in as damaging the old ones. At least you can take great care with alignment when parting and joining to try and avoid damage, with new components you are a complete hostage to fortune, as you found with your release bearing, and one thing you don't want is anything inside the bell-housing failing shortly after putting it all back together.

Was your failed bearing pinned as in that link I gave? I would only ever buy Borg and Beck clutch parts, not no-name after-market. Even Q&H are said to be a bit iffy.
PaulH Solihull

Yes, old bearing was pinned but i don't recall whether the new one was or not. i'll soon find out.

Side note; the oil that comes out of the hole at bottom of bell housing is black which make me think the bearing is wearing already? there is fresh oil in both the trans and the engine and i cleaned the inside of the bell housing thoroughly before re assembly.
Rear engine seal did not show any signs of leaking but i did not remove clutch. Altho i don't remember looking to closely at trans i do remember seeing some oil on the floor when i had separated the two and briefly had the trans standing vertical on a couple of blocks.
What would cause it to only come out when you shut the engine down?
Dennis Silance

As I say, when the engine is running there is negative pressure in the crankcase, which will tend to pull air in through a leaky seal and hence stop oil running out. With the engine stopped that negative pressure goes away, and in fact with heat soak could become slightly positive pressure, which would be more likely to push oil out. At the very least the loss of negative pressure would be more likely to allow any oil that is around the seal to run out. Wouldn't have thought you would have got much though, just what was lying round the seal. But then again I don't know if there any wells around the seal that would hold a larger quantity. If the oil dripping out is blacker than what is on the dipstick then it quite possibly is picking up carbon, but whether that is from the earlier failed bearing, or the new one, would depend on how carefully you cleaned the bell-housing and engine backplate. As you left the clutch in place hence couldn't clean behind it (I assume), it could well be from the failed bearing.
PaulH Solihull

Well I've decided to bite the bullet and pull the engine today to change the bearing.

I've not been able to find a definitive answer or source for a sure-fire reliable bearing, so I've scoured eBay and found a "new / old stock" Quinton Hazel carbon bearing. Thing is how old is "old" especially bearing in mind Paul's comments above re recent Quinton Hazel bearings. The box looks quite old and it was also listed as suitable for a Humber Sceptre, so my hunch is is probably pre-dates the era of shoddy quality. I've also not been able to find much information on the box part number so this may also indicate obsolete stock? One thing's for sure, it's not the riveted type bearing so I'm reasonably confident this one should is of better quality.

I'll report back later, with pictures, on what I find when I pull the old bearing. It's now noisy after just a few minutes from cold and I think it's at the stage now where I the car is telling me "I can't take much more of this pain!"
Mike

Short update: After my last post on this thread I have driven from Norway through Denmark, to MGLive at Silverstone, to Wales, back again with final stop in Abingdon, through Denmark again and home to Oslo.

Not one single squeak from the clutch! Strange, isnīt it?

Tore
Tore

This thread was discussed between 07/06/2012 and 07/07/2012

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now