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MG MGB Technical - Graunch when Clutch Pedal Depressed

Just been out getting some miles on the new engine to run it in, 40 miles in and 1 ml short of my turnround point it started to make an odd noise. Managed to get home but symptoms are:
• 80% ish of the time on depressing the clutch, still in gear, not touching the gear lever, it sounds like you are trying to get into gear without the clutch fully depressed – but as I say it is in gear and the lever has not been touched
• I can change gear OK
• The noise stops when the clutch is at the biting point or thereabouts.
Any thoughts before I pull the engine again……
All the clutch parts are new, and I have a carbon release bearing
Mike Dixon

Hmm, doesn't sound good but sometimes things take time and use to settle in, I'm not sure if you meant your journey or your running-in so far was 40 miles.

But a check of easy stuff first is er, easy, so why not. If you put on a new rubber gear lever grommet check it's not too tight I've had one that took the lever out of gear on the overrun.

Check the looseness or tightness of gear lever fixings locators.

Gear oil level.

Clutch pedal for freeness, tightness, ovalling, pedal bush, return spring, pushrod and clevis pin condition, master cylinder fluid level and condition.

Drive the car more to see if it improves or gets worse.

Then it's checking under the car, movement of slave push rod and clutch arm while pedal is operated. Can you see the other end of the clutch arm and release bearing movement.

Check or bleed clutch fluid.

That's me out of ideas.

Nigel Atkins

Sounds a bit like a dry spigot bush in the rear of the crankshaft ---from here
William Revit

If it only does it in gear (engine running) and never when not in a gear then it sounds like the spigot bush as said. If it does it in both situations then probably release bearing issues.

I've had many weird noises when both graphite and roller bearing types were in the process of failing. Graphite in now, but very very occasionally it will make a squawk when pushing the pedal down. I found my release arm was positioning the bearing was off centre to the first motion shaft - someone who works on these cars every day said they are all like that to some extent - and I put the failures of both types down to that. Centred now, six years ago, so time will tell.






paulh4

No visible obvious issues

My engine builder came out this morning, really good of him, to have a test drive and after a chat with Gearlink, our local gearbox gurus, they are certain it is a clutch issue either the spigot bush or a fault in the pressure plate

The Engine just about ready to lift again, hopefully we will be able to spot what the issue is; I will report back!
Mike Dixon

Just had my engine builder out to have a look as I could see nothing obvious.


- Release bearing ( carbon ) looks fine - I wonder if I should try a roller one?
- Spigot bearing is OK
- Pressure plate OK ( it was suggested by Gearlink loose springs might be the problem) it is an 8 inch plate, slightly larger than standard but should not be an issue?
- First motion shaft looks OK

We wondered if it could be the main shaft spinning inside the gearbox. We did think of having a look and got as far as draining the box and starting to remove the front cover but decided to sleep on it - if all else fails I will need to get it to a garage.

I was hoping it would be something obvious once the engine was out so it’s all very frustrating.

Might the fact it has only done it when hot ( with very limited 'testing' - 2 trips) be a clue?



Mike Dixon

Mike
Just a possible--
Sometimes--depending on the brand--the oversize clutch plate can be a mismatch to the clutch cover of also sometimes the flywheel
Have a real good look at the matching of the plate to the flywheel, sometimes the spring retaining plate rivets or the bent out spring retainers are at too large a diameter or poke out too far and won't quite fit in the recess in the flywheel--a slight machining out of the flywheel fixes that-or a different brand plate
Also same with the plate fit to the cover, make sure there is clearance inside the inside diameter of the cover surface for the spring retaining plate/rivets to clear, sometimes with some plates the rivets will foul against the surface here and/or the same spot on the flywheel and also that the outside diameter of the plate hasn't been touching the cover---some covers are only just not quite large enough for the larger plate

Also was the crank bush lubed ok

I doubt it's the gearbox if it goes away when the clutch pedal is fully released, -normally if it's gearbox you hear it all the time, it'll be something with that clutch plate --or a dry bush in the crank--I thinks

willy
William Revit

"but as I say it is in gear"

If it's in gear with the wheels on the ground and the car not moving then the first motion shaft isn't spinning.

I'm assuming it only happens when the engine is running.

The other possibility is worn thrust washers on the crank so it's being pushed forwards as the clutch is disengaged. But grinding like gear 'teeth' would be pretty horrendous.

As said before if it _only_ does it in gear then it's more likely to be the pilot bearing. If it does it in and out of gear then more likely to be the release bearing or cover plate. I've heard of graphite release bearings breaking up in a few dozen miles when the graphite ring was pinned into the casting instead of bonded, and also of the release ring on the cover plate breaking free in a similarly short time. Pull the release arm gaiter back and you should be able to see part of the bearing, and all of the release ring when the engine is turned. With a 'new' release bearing you should be able to see a gap between the bearing casting and the release ring where the graphite on a new bearing protrudes.
paulh4

Mike-
Inspect both the pivot hole inside of the end of the actuating rod of the clutch slave cylinder, as well as the clevis pin for signs of wear. It is common for both the actuating rod of the clutch slave cylinder and the clevis pin to have to be replaced. Next, inspect both the smooth shank of the machine-grade pivot bolt (BMC Part # 11G 3196, Moss Motors Part # 190-550) and the sintered bronze alloy Oilite pivot bushing (BMC Part # 11G 3195, Moss Motors Part # 330-200) of the clutch release lever (Three-synchro transmission BMC Part # 22B 56, Moss Motors Part # 190-580; Four-synchro transmission BMC Part # 22H 1056, Moss Motors Part # 462-590) for wear. Sometimes clutch release problems are not caused by the hydraulics, but instead by wear in the mechanical parts. The clutch release lever is carried on a sintered bronze alloy Oilite pivot bushing that pivots on a smooth-shanked machine-grade pivot bolt. After many thousands of miles, it is not surprising that it can wear, causing it to become loose, resulting in lost motion in the release process. Wear of these components can affect the amount of throw that the slave cylinder actually applies to the carbon clutch release bearing. If the first part of your pedal movement is just to take up the wear in the pivot bolt, it means that you may not have sufficient movement left to operate the hydraulics fully. The clutch driven plate/friction disc can disengage enough to permit shifting, yet still be allowing excessive friction on the clutch driven plate/friction disc, resulting in rapid wear. In addition, if either the sintered bronze alloy Oilite pivot bushing and/or ends of the smooth shank of the machine-grade pivot bolt are unevenly worn, the clutch release lever will then tilt when under pressure from the actuating rod of the clutch slave cylinder, causing both off-center running and uneven engagement of the carbon clutch release bearing. This will cause a grinding sound. Replace both the sintered bronze alloy Oilite pivot bushing and the smooth-shanked machine-grade pivot bolt if any wear is found, and be sure to install a new 9/16"-18 UNF Nyloc nut in order to secure them in place. Make sure that the new sintered bronze alloy Oilite bushings are relieved at their ends in order to aid in pressing them in. Their replacement will reduce free-play/end-float in the action of the clutch pedal, making engagement of the clutch more consistent.
Stephen Strange

Quick update on this one. In addition to the very useful suggestions above, most of which I have checked, I had long chats with some transmission specialists - thank you Gearlink, Hardy Engineering and Heathrow Transmissions, who were all really helpful - and all said it's the clutch.

The clutch supplier, Precision Clutches in Dorset offered to have a look at it so I took it down to him, but he could see no obvious witness marks or faults. He did however replace the pressure plate and rebuilt the cover while I waited. Great service

Engine back in - over an hour just to get in in place this time, that will teach me to think we were getting quicker - and 70 miles later all is well.

So, so far so good, fingers crossed!

Thank you all for your advice and support, this a great resource late at night when I am beginning to despair!

Mike Dixon

A quick update on the clutch and seeking any thoughts you might have.

With the graunch still there albeit a bit better and more intermittent we got an endoscope up into the bell housing again. The carbon release bearing, 1000 miles in, is now showing some very odd signs of wear; it has seemingly worn into the arms on the cover so that it has a series of very pronounced ‘teeth’ on the face of the bearing. I will try and get a photo in the morning - the one I have is not good

We also noted that the release fork jumped up and down/vibrated a bit as the clutch was used - is this normal? I did note a little release fork play in the bolt when I fitted it even when putting the old one back in which was a tighter fit than the new one I had bought. I had fitted a new bush.

Also the revs sometimes drop when the clutch is depressed.

So any ideas about the wear? I am certainly not riding the clutch but have had some 'fun' with the slave cylinder and bleeding the clutch.

So it looks like a minimum of the new release bearing - I am now tempted by a roller one, despite the reticence of some to use them


Any ideas about the wear? Better to try and sort that out before I fit anything

Mike Dixon

Mike,
unfortunately if new parts have been fitted and there are problems the new parts are likely suspects. Having play in the new bolt but not old bolt but then you have a new bush too, how does either bolt fit the old bush.

What condition is your clutch slave push rod hole and clevis pin in, same for master cylinder, pedal hole and bush.

Are the release bearing clips sitting correctly.

The release fork not bent or cracked.

Despite having lots of clutch problems from getting my gearbox conversion from a con-artist I'm not a clutch expert, or on anything else, but your description of the condition of the release bearing to me suggests something is wrong, either bearing over throwing or clutch too proud for whatever reason, the carbon is very soft though.

At idle the revs drop when I put my clutch in which AFAIK is correct.

Willy's the mechanic, I'm not sure you'd normally see much movement from the release fork other than slight at take up of the clutch.
Nigel Atkins

Mike
I might be reading this wrong but are you saying the carbon thrust is running directly onto the arms of the pressure plate (cover)
There should be a rubbing pad on the arms(fingers) for the thrust bearing to rub against---If that's not there then that is your problem--there are some aftermarket covers that don't use the pad but 'have to' use a bull nosed roller release bearing---maybe they've sold you the wrong mixture---You can run a roller bearing on both types but you can't run a carbon bearing on the non-pad type
Here's pics of the 2 types

First the original with the rubbing pad----

https://www.sparesbox.com.au/part/clutch-industries-standard-replacement-clutch-kit-r114n?gclid=Cj0KCQjw_4-SBhCgARIsAAlegrUwsWrpvl5ttsWTg2XnFG53OmiXkBMoTF0sHU4g7vR8Dr4UyOzBfQ4aAma6EALw_wcB

and secondly the type without the pad which runs a roller bearing-

https://clutchdirect.com.au/products/v114n-15164?currency=AUD&variant=32487776026709&utm_medium=cpc&utm_source=google&utm_campaign=Google%20Shopping&gclid=Cj0KCQjw_4-SBhCgARIsAAlegrXjMgh4pz6gzenZdzRIPdsK3Op58kRP9fBAcek81JBLdzqsmwmNhlUaApQbEALw_wcB

willy
William Revit

As Willy roller-bearing release bearings can run directly on the fingers of the springs (MGB V8 and 1500 midget for example, 1st pic) but graphite need a release ring attached to the fingers (2nd pic).

If the release arm moves about as the clutch is operated it implies the pivot is worn, but if the bearing had developed 'teeth' from running directly on the fingers then that may be the prime cause, and of vibration.

It's 'normal' for the revs to drop with a graphite bearing as opposed to a roller bearing. Some say theirs drops by a couple of hundred rpm but since going back to graphite mine only makes a barely audible change with no change on the tach.

The biggest problem with graphite is if the bearing is not concentric with the gearbox shaft as in the pictures I posted on 13th March. That misalignment wrecked a roller bearing eventually, after a previous graphite one.

Engine out, I suspect.






paulh4

Thanks for that. Just spoken to my clutch supplier, he says it is ok to have the rubbing pad ( which I have fitted) with a roller bearing. Good job I called because:

As a result of my call to him yesterday to discuss the odd wear he dug out my old rubbing plate which he had not yet discarded post the cover rebuild and on closer inspection he noted some slight 'burn marks' on it ( it had only done 200 miles or so at this point and the carbon bearing looked fine) ) so it seems the issue is the bearing being in constant contact with the cover as suspected above.

So engine out and sort out the fork - I have ordered a recon one just in case.

How much play in the bolt/bush is acceptable?

Mike


Mike Dixon

It'll be interesting to see what everything looks like when you get him out Mike---maybe a pic or two if you feel inclined

willy
William Revit

The release bearing is _always_ in contact with the cover plate.

There is a spring inside the slave that is constantly trying to push the piston out when the clutch is released. This takes up any play in the mechanical components at that end of the system so you get a consistent biting point, even as particularly the graphite release bearing wears down. If that didn't happen the biting point would get lower and lower.

For that reason mechanical wear at the slave end particularly at the clevis pin, push-rod and release arm has no effect on clutch operation, and the length of the push-rod isn't critical either.

That's not the case at the pedal end, wear there _does_ result in a lowered biting point.

Up to a point play in the release arm pivots isn't critical either, but lateral offset of the bearing to the shaft can be.
paulh4

I have managed to get some pictures, hopefully you can see what the 'teeth' look like

So if the bearing is always in contact, what might be causing this?







Mike Dixon

At first sight you have the wrong cover plate without the release ring. But how sure are you that is not the release ring attached to the springs? Those 'teeth' look far too pronounced to me to be worn into the graphite.

Push the release arm towards the slave piston i.e. move the push-rod further in, that will do two things.

The first being to retract the release bearing. If the thing with teeth stays where it is then it's part of the cover plate ... or the release bearing has become detached from the release arm.

Another possibility is that the release arm may not be coming back far enough in normal use so it's pressing the bearing too hard against the cover plate, which could be because the push-rod is too long and the piston is bottomed in the cylinder, or the master piston isn't coming back far enough to release pressure from heat expansion of the fluid. If you can move the push-rod further in to the slave then neither of those things are happening as the piston is being pushed further into the cylinder and displaced fluid is going into the reservoir.
paulh4

Hmm-the teeth are the locators to stop the rubbing pad from spinning/slipping on the fingers, there are a few different methods of doing that, some have straps riveted to them ,others don't seem to have anything
As Paul says the carbon thrust will always have 0 clearance and rubs against the pad at all times, and must have travel left in the slave cylinder
It's difficult to see the makeup of your thrust bearing from the pics but the pad appears to be much smaller in diameter than the thrust from what I see there---I think you'll be pulling it out again--before you do just push that clutch lever back towards the slave cyl. to make sure it has clearance and will push in -If you do pull it out you can put a straightedge accross the face of the pad in a few different spots with the cover still bolted up to make sure it's running square and check the size of it compared to the carbon thrust
I take it that it's the same gearbox/clutch fork as before the engine job

willy
William Revit

Thanks both you are right, the teeth are part of the wearing pad so stay put when the release bearing comes back - Doh! It come back at a guess about 1cm?

I think the pad may be a fraction smaller than the thrust carbon, but if it is it is a tiny amount.

The piston does move into the slave but does not com back a huge amount - local mechanic is coming round on his way home to have a look.




Mike Dixon

Shoulda looked at my knackered cover plate with unused graphite bearing.

Yes those teeth are definitely the release ring, which on mine is retained by a crimped-on flanged ring on the other side of the springs.

The other way to tell of course is to turn the engine while looking - the release ring will rotate with the spring fingers while the (graphite) release bearing doesn't.

Crossed in the ether.

Push rod should really come back out to take up all the play, but I doubt that is any part of your problem, it will do so as soon as you operate the clutch pedal but may need a couple of pumps before you would be able to engage a gear cleanly and get the right biting point.






paulh4

I also note the release ring is not circular so will not match or even cover the thrust pad all of the way round?
Mike Dixon

Indeed, as pictured earlier it is 'triangular' for some reason. The non-overlap is negligible though.
paulh4

When the engine job was done, did the spigot bush get replaced or is it the original--
If it was replaced, was it an oilite/sintered bronze bush or has someone used a straight bronze/brass bush
If it's not a sintered bush it will sqwark and probably seize on a long trip

just to get it straight in my head--
No noise without the engine running
No noise if the gearlever is in neutral and engine running
In gear engine running--noisy as you let the clutch up until the bight point then ok

it does sound like a bush issue, wish it wasn't half a world away--a graunch to you might be a squeak to someone else or around the other way
Can you feel any vibration at all when it happens through the clutch pedal

willy
William Revit

Willy

You are right - it only happens with the engine running and with the clutch depressed. If you then raise it to the biting point and depress it again the noise has gone. it will be like that for a short period - immediate subsequent depressions to change gear are noise/vibration free.

My engine builder did not replace the spigot bush but when we removed the engine it was checked again and declared OK.

As you say one man's graunch is another's squeak. It was embarrassingly dreadful at first but has certainly got quieter to the degree it is often just the vibration

Trouble is it is intermittent and has a habit of disappearing when you get anyone to listen to it!

Mike
Mike Dixon

Did you clean and lubricate the bush, shaft (plain section and splines) and pivot points with pukka clutch grease?

I'm still not exactly clear when the noise happens - i.e. as you are moving the clutch pedal, or when you are holding the pedal still i.e. in gear at the biting point before moving, or ... something else.

Also is it only at a standstill about to move off, or when changing gear when moving? The former will have the pilot bearing rotating on the stationary shaft, but whilst there will be some rotation in the latter circumstance it will be much less.

My misaligned roller bearing made noises on and off for years with vibrations coming up the pedal as I operated and released it. The new now concentric graphite bearing has made a very slight noise while depressing the pedal to change gear on about three occasions in six years, but so rarely and so long ago now I can't recall if there was a vibration in the pedal as well.

paulh4

So just to be clear, this is the same crank/bush that was in your car before the engine rebuild or is it another engine---

That rubbing pad --yours has the teeth to locate it but some have 3 straps riveted to them instead to locate them-that's where that triangle shape comes from to accept the straps

I can relate to-
"Trouble is it is intermittent and has a habit of disappearing when you get anyone to listen to it! "
I used to do some diagnostic work for a new car dealership and it amazed some owners that their issue seemed to disappear when they drove in the door- they couldn't get their head around the fact that it was a car and sh*t happens, even when they're new
William Revit

Paul,

The release bearing shafts were greased with Castrol Moly, there was some LM on the input shaft - so that might need doing?

The noise only happens when you are changing gear when moving and depress the pedal to change gear.

It happens at the bottom of the clutch depression before moving the gear stick - there is also a slight vibration in the clutch pedal. On lifting the pedal it stops and does not re-occur when you put it back down straight away

It has not happened when moving off.

Just been out for quick 40- miles, virtually nothing

Decision time soon - it needs to come out this weekend, for a mechanic to look it over on Monday if I am going do do anything prior to our 3000 mile rally.

All the parts I may need ( less grease!) are inbound, to carry with us if nothing else. Any hints on what to get ideally at either Halfords or Euro car parts if Moly is not good enough?






Mike Dixon

Mine has a 'triangular' release ring but it is retained by a crimped-on flanged collar on the back as previously pictured. This makes it free to rattle with the clearances between the 'teeth' and the spring fingers. No straps.

I used Sachs clutch grease, previous kits had come with a sachet but not the one for the V8 and I was wary about using general purpose grease. Copper grease for example I find goes very sticky, and for a long time the gearbox shaft had been dragging in the pilot bearing which made selecting gears at a standstill difficult. When parted both parts had thick black gunge on them that took some shifting, been OK since.

If it only happens when underway changing gear and not prior to moving off then I feel it's less likely to be the pilot bearing.

If it only happened while the clutch pedal was being depressed I'd have said it was linkages from slave to release bearing. But if it is only when the pedal is fully depressed that is more like parts of the release bearing or release arm rubbing on something they shouldn't. My roadster did that for a long time before the release bearing casting finally wore through and broke, so I didn't fully depress the pedal! With that happening only underway it makes it sound like something is rubbing on the gearbox shaft rather than the clutch cover plate as mine was.

It's a beggar. With what you have coming up it probably would be best to get the engine out, and look very carefully for signs of rubbing.
paulh4

I'm wondering, and this is a longshot, that because the clutch plate is new (and fat) that the fingers of the pressure plate will be sitting down further than usual/normal--the rest position of the fingers gradually rises out towards the carbon thrust as the drive plate wears-- Being in this lower position because it's new, 'maybe' the collar part on the inside of the rubbing pad might be just touching the splined hub part of the drive plate when the pedal is fully depressed, if it is this it will correct itself as it wears in-
Maybe go for a drive and not fully depress the clutch pedal and see if it doesn't happen then-
If there's no noise like that I'd be tempted to live with it and it'll disappear with time as it settles in-
William Revit

I am coming round to pulling the engine for a look - at least I will have done all I can even if it fails in the middle of the trip.

When I was waiting for the cover to be rebuilt I saw a notice saying any use of Copper grease in installation would invalidate the warranty

I am sure I can cadge a drop of sachs or similar from somewhere.
Mike Dixon

Crossed in the ether. It is only when going past the biting point, if not right at the bottom of the travel that the noise occurs
Mike Dixon

Hmm -that really does sound like the spigot bush then----If you're going to pull the engine out it'd just about be worth throwing a new one at it---but make sure it's a sintered bronze one if you do and fill it up with oil properly before you fit it--or flood the one you have with oil while the engine's out
Possibly, The crank might have had a swim in a hot tank while at the engine mans and washed all the lube out of the bush----------?

The clutch guys probably don't like copper grease, specially if there were too much on the shaft spline as it travels everywhere from anything spinning---All you need on the spline is a smear of oil to stop it rusting up, just a wipe with a damp oiled rag is enough there
Something I thought of but probably not it-when pressure plates are new sometimes they have a rustproofing protective coating on the surface that has to be cleaned off--If you don't clean it off it can cause vibratey noisy clutch noise at that takeup point but it doesn't do it for long just the first few times moving off ,so probably not that, but if you're going to pull it all apart maybe a wipeover with some thinners or silicanoff or brake cleaner could be an idea

willy
William Revit

Getting confused here:

"It happens at the bottom of the clutch depression before moving the gear stick"

"It is only when going past the biting point, if not right at the bottom of the travel that the noise occurs"

Should 'if not' say something else?
paulh4

Sorry; The noise starts at the biting point and continues while held there or at the limit of depression

Vice versa coming up - it stops at the biting point
Mike Dixon

OK. Something rubbing where it shouldn't be, or vibration between the release bearing and cover-plate. Can't see it being the pressure plate if it happens with the pedal fully down. I go for thoroughly cleaning the release ring and a new release bearing, also degreased before fitting.

If you maintain a steady speed, hold the throttle steady, then use the clutch does it happen then? I appreciate it's probably not happening much especially now, but if no noise then, only when the revs drop when changing gear, it would point to the pilot bearing as the two halves should be rotating at the same speed. If it still makes the noise then release bearing/cover plate.
paulh4

A small vibration at the pedal usually indicates the pad is running out of true. This usually results in accelerated wear of the release bearing. Use the straight edge as above, comparing distance to the engine backplate on either side. We have found even new reputable brands of clutches are not immune to this fault.

To the list of things that can cause excessive residual contact pressure on the release bearing, add clutch hose breaking down internally and partially acting as a one way valve.

We had a new pivot bolt for the clutch arm measure up at 10 thou undersize, smaller than the worn one it was to replace. Fortunately this is an outlier, but it pays to check.

As to the source of the noise, I'm with Willy: spigot bush. If the crank was tanked and the bush not renewed that would do it. Even if in doubt it is well worth putting in a new (pre-lubed) bush if the clutch is out and apart, just in case.
Paul Walbran

I have just pulled the engine and found that the release bearing is starting to break up on the upper edge - from about 10 o'clock to 3 o'clock as you look at it.

The right hand retaining spring had rotated free as shown in the photo, despite me tightening it up

I attach a couple of pictures - any thoughts?

I will do the straight edge thing shortly on the release pad










Mike Dixon

The breaking up could well be due to the bearing rattling around and misalignment if one of the clips was not in the correct position.

When I've fitted these I've reused the springs and they very definitely snap into position. If one needed tightening it may have lost its tension and should be replaced - do both as well as a new bearing. I see some places show a wire retainer with roller-bearing types.
paulh4

Thanks - there is also a bit of play around the fork bolt, not a huge amount. As Paul W noted the supplied bolt was even looser than the in-place one which I re-fitted

Mike Dixon

Never seen a thrust like that before, they usually wear flat accross the face---i'm thinking it's just a dud one, and although it's not ideal I can't see that making your noise, there's nothing in there in that area for that to be rubbing on to cause that I still suspect the spigot bush
With the clip did you get that right around on the flat on the back originally, more or less opposite where it is in the pic-?--bit unusual that it spun around if it was locked in place
Any chance of a pic ot the pad on the pressure plate----
William Revit

As well using as using a straight-edge across the release ring to check it is square with the back-plate - in several positions i.e. vertically, horizontally, 45 degrees to one or other and so on, do the same across the bell-housing to the face of the release bearing. Unless both are 'true' the pressure of the clutch will be taken on the outer edge of the graphite, not evenly across the whole surface, which could cause it to break up like that while it attempts to 'wear flat'. It can pivot one way in compensation but not the other.
paulh4

Picture of pad attached. First go at measuring how square it is, there may be 1mm top to bottom, but it's difficult to tell - would a dial gauge work? I will give it another go after lunch

Struggling a bit with the release bearing measurement - it keeps moving!

I had thought the clip was locked in place but obviously not. I struggle to see how that part of the carbon face is making contact with anything to cause that damage?


Mike Dixon

Bugger, I was hoping to see something unusual but no, honestly I don't think the carbon bearing is an issue, yeah it's lost the edge off it but it might have been dropped or faulty before you got it--If it was mine, maybe a new one would be best practice but I'd be tempted to reuse it---
To measure the rubbing pad on the pressure plate, if you push something straight accross it and measure the gap from the engine backplate out near the ringgear to the straightedge on either side- try in a few different positions--If all your measurements are within say, 1/4" then it should be ok--it doesn't have to be perfect with a diaphram clutch, if it was out enough to be an issue you would feel it through the pedal every time you started to depress it-
My money's on that spigot bush-----------If it's in good nick then a good soak in oil-
With the clutch off , if you get a piece of rag to make a plug and hold it up against the bush then fill the bush right up with oil, plug it up and leave it for an hour or two to soak in, then unplug it and wipe your mess up, clean the flywheel face pressure plate face and the clutch plate with brake cleaner and bolt it back together-
Apart from that I'm running out of ideas

willy
William Revit

Lay the straight-edge across the bell-housing in line with the bearing pivots, then I'd have thought a rule from that to the bearing right over the centre-lines of the pivots would do the job.

I wouldn't have thought 1mm at the release ring would have been a problem, but then I've never measured one! In any event being positioned by the spring fingers it's likely to correct itself to the release bearing as the clutch is disengaged.

You say it has a larger pressure plate, is it a 'heavy duty' with stronger springs? If so then maybe you need a 'roller' bearing.
paulh4

I have just looked into the clutch cover again and had a poke around and there is a bush floating around in there between the cover and the engine - could be the the spigot bush? It's about 1/2 - 3/4 inch long and the same diameter as the input shaft. Odd as when we looked last time and had the clutch off everything was where it should be. It might account for the grating

Are there any bushes in the clutch construction? I think I am going to have to pop off the clutch and have a look.

The carbon break up may be a separate issue?

I do have heavy duty springs so will look at a roller bearing


Bit of a saga this.......

Mike Dixon

Now you're talking, my guess is the bush was dry enough to grab on the shaft when the shaft got warm then spun in the crank
New bush-
Actually, there are two lengths 1" and 1 1/2" the long one for 65-67 3syncro box and the shorter for 68-80 You'll need to measure the depth of the machined tunnel in your crank to see if it'll take the longer one if there's been some part swapping and give the spigot on the gearbox shaft a nice polish up, it might have bits of bronze stuck to it
There's a foolproof method for oiling the new bush, I'll get some pics up for you
William Revit

Bingo. Not having changed one, I assume it should be something of an interference fit in the crank? In other words, make sure the new one isn't loose!
paulh4

Mike
When you get your new bush, --They're known as self lubricating bushes, which they are, but they need to be filled before fitting to the crank-
The recognised way to do this is to leave them bathed in oil overnight and the oil soaks in, but if you're impatient like me there is a way-

pic #1 --place the bush upright on your hand and fill it up with oil, then,

pic#2 --push on it as hard as you can with your other hand/thumb, after probably 20 seconds or so the oil will start to weep through

pic#3 --keep pushing

pic#4 --push until there's a full covering of oil on the outside, only then will the bush be fully loaded

Now it's ready to fit, wipe the oil off the outside only, find a decent flat washer to fit accross the end of it and drive it in with a punch or socket and bar, etc until it's flush with the end of the crankshaft






William Revit

3&4

Yeah bit of a nuisance having to pull your engine out but i look at stuff like this as a part of the journey, just another day of your life-----------





William Revit

I think you are right - it only happened when the car was really warmed up. The old one is a gentle fit and slides in and out quite happily

Just got the new bush, having been assured it the one I was after when I got there it is the long one ' but they cut down easy enough' to get the 1" one I need. My engine builder is doing that this afternoon.

I think I have oiled it - that trick needs a bit of a knack!
Mike Dixon

Might pay to redo it when you get it back just in case they are too helpful and wash it out for you
William Revit

Mike,
on one of the occasions the engine was out on my Midget for yet another clutch problem I thought I saw only one wire clip fitted when it should have been (two) sheet type clips but I was told having only one wire clip wouldn't have mattered anyway.

Whilst you've got this far I'd suggest you do fully check the release arm and have the bolt and bush as a good fit same with slave, master and pedal, and good point by PaulW about hose, otherwise any small discrepancy or noise from the clutch will have you jittery for a good while thinking what's that, not again. This time you want to be able to fit and forget about it not listening out every time you drive the car.
Nigel Atkins

I got it back in my jar of oil and he was aware of what I was up to so it should be OK

I have replaced the fork bush and the bolt is a good fit, the pedal bush was replaced by PO not many miles ago, slave and master are new as are the copper pipe and hose - all of them were fairly worn out. Hopefully I have covered all of the bases.

One query - the parts book and every photo I see have the release bearing fork bolt coming up from the bottom. When fitting bolts as a general rule I always to is the other way round , my logic being if the nut does by chance come off at least there is a fighting chance the bolt will stay there?
Mike Dixon

Mike,
sorry to worry you but that's my logic too. Parts drawings even in WSM can be wrong, or different. The parts book for the Spridget clutch also shows a locking tab washer to the bolt head but I can't see how it'd work, perhaps a left over from earlier car/model applications.

I follow the same logic with an exhaust hanging clamp that fixes to a rubber block mount and have the clamp resting on the mount with bolt through from top where as parts shows clamp under and bolt from bottom.
Nigel Atkins

there's a reason it won't go in from the top, I think the bolthead jams on the bellhousing, or the top hole is smaller dia or something, i know i went to do it once for the gravity reason you mention but it wouldn't go--
William Revit

The ones I've done have been bottom up, can't remember if I tried top down or not. Haynes is bottom up, but the photo is upside down, probably because they went by the bolt! If it goes in that way then no reason why you shouldn't use it as far as I can see.
paulh4

IIRC, which is so difficult as so many things happen to my cars, I put the exhaust clamp with it on top and bolt from top after a copper/brass/other(?) aeronut came loose on it (IIRC).

The u-bolts nuts holding on my s/s exhaust together occasionally loosen slightly giving a warning blow from the exhaust and someone suggested using aeronuts as they would come loose.
Nigel Atkins

You are right - the bold head fouls bell housing from the top, it has to go in from the bottom

Now carefully grinding down the new release bearing so it fits in the fork so I can get the spring clips in.......
Mike Dixon

That's a bit unusual to have to grind the thing, but if it has to be it has to be----Some release bearings come with different style clips, like a wire f clip , they have a hole in the end of the protruding round shaft pieces and straight piece of the wire clip goes in there and the f shaped piece clips around the back of the fork-They're probably a slightly wider one to make up for the room used by the tin clips---i'd be doing what you're doing, much better setup
William Revit

The two I've seen.






Nigel Atkins

Having to grind the release bearing doesn't sound right and not something I've ever had to do. Is this another new bearing? If so did you have to do that with the previous one as well? I wondered before if you could have the wrong release arm, 3-synch and 4-synch are different, albeit the bearings are the same.
paulh4

The issue with the bearings is that the units made for the wire retaining clips are slightly wider than the tin clip ones--Unfortunately they don't always supply the wire clips and also when they do the clips won't clip onto 'some' arms
If it happens to be a plastic bodied roller bearing they actually press into some arms that have a slightly over half shape where the pivots push into and don't need clips-but for arms that are only half round where the throwout sits they need clips and if the wire clips (that probably weren't supplied) won't fit the arm properly, reducing the width of the bearing carrier to take the tin clips is the best option rather than opening out the fork which wrecks it for future bearing choices

Nigel--You were up late last night young man
William Revit

Willy,
because I am young. 😁
Nigel Atkins

The old carbon bearing fits perfectly in the new fork and allows space for clips but the new one is too tight to get even one flat metal spring/tin clip in. There are no holes in the end for the wire type clips.

I decided to grind the bearing rather than the fork for onwards compatibility as Willy notes. All done but it was a bit of a faff.

I have to say there is far less play now in the fork/bearing/cotter pin

All back in, 40 miles this afternoon and so far so good
Mike Dixon

You're the man Mike--you deserve a good result for sticking with it-

willy
William Revit

Thanks Willy, the support from here has helped a huge amount, it has been a bit of a saga!

Mike
Mike Dixon

Believe me things can be a l-o-t worse but as Willy well done for sticking with it and sorting it.
Nigel Atkins

Mike-
If you are worried about the nut coming off and losing the pivot bolt, install a new 9/16"-18 UNF Nyloc nut in order to secure it in place.
Stephen Strange

This thread was discussed between 13/03/2022 and 09/04/2022

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