Clutch thrust bearing & diaphragm wear

[Cam]

While my engine is out I was wondering if I should replace my clutch and thrust bearing as they seem a bit worn. Well, the clutch plate is fine but the diaphragm seems a bit worn and so does the corresponding mating face on the thrust bearing.

I have not had much to do with these type of clutches, so I wondered if someone in the know could have a look at these pictures and tell me if this level of wear is OK. I know the pictures are not brilliant but it's all I have to hand at the moment.

Thrust bearing now:



Thrust bearing new:



Clutch diaphragm new:



Clutch diaphragm now:



The finger ends (shiney bits) do seem to be thinner than the rest of the fingers.

So, I just wondered if it would be OK to carry on with these parts as is, or replace them (more cost!) while the engine is out etc.

[Alec]

Hello Cam,
what does the thrust bearing feel like, as it appears as though it may be tight?
I would not normally expect much wear on either the diaphragm finger ends or the bearing front face.
As to replacing them, well I would, but it depends on your mileage, reliance on the car and how adept you are at removing the gearbox versus cost.
If there is any doubt, however, about the freeness of the thrust bearing, I would certainly change that.

Alec

[rayofleamington]

They still 'look' serviceable but you shouldn't have significant wear so early, (and it's hard to tell the life of a bearing by looking)
The roller type bearings rely on being central to the clutch otherwise the fingers get a cross axial movement relative to the release bearing face (under full load at 1500 to 2500 rpm it creates a lot of wear to the bearing face and the fingers).

It would be worth putting the release lever to the point where it's just about to open the clutch and see if the bearing is off centre to the input shaft.
To find that position without rebuilding the car, measure the height of the clutch fingers from the engine endplate. Then subtract approx 5 mm (release bearing travel is normally only approx 7mm) gixing value 'x'mm
Push the release bearing so it is 'x'mm back from the mounting face of the bellhousing.

If it looks way out of concentricity, then your release lever ought to be modified

[Cam]

Alec,
The thrust bearing does not feel tight at all, it spins quite freely (but not too freely!).

I have done about 20,000 miles in the car with those bits so it is wearing a bit fast! I don't want the car to break down a lot, but it's not the end of the world as I have other cars for transport..... I don't mind replacing the units later on as I don't have a problem with taking engines and gearboxes out, I have my own hoist and I have done it many times.

Ray,
I think you may have hit the nail on the head with that one!

You said:

The roller type bearings rely on being central to the clutch otherwise the fingers get a cross axial movement relative to the release bearing face

The pivot for the clutch arm which was given to me by the Birmingham Minor centre simply had a hole in it for the pivot and they removed the sleeve that fits over the gearbox input shaft that the bearing usually rides on, so when the bearing mates to the clutch diaphragm it does so in an arc and not straight on. This has also led me to believe that this has been causing the bad clutch judder in 1st and reverse that I have been experiencing. (due to un-even pressure on the fingers).

I spoke to them about this problem and they say that 'NOW' they have investigated this problem and in retrospect it would be better to leave the sleeve on the gearbox input shaft (for even mating of the bearing to the diaphragm) and to slot the pivot bracket to allow for the movement of the arm. Apparently this method was tried by Ewan of the Minor centre and it seems to work OK without any clutch judder.

The only thing that worries me is the stresses placed on the guide tube.

I think that the bad wear in such a short time was due to the axial movement of the bearing relative to the diaphragm, which should not be an issue with the guide tube in place.

[turbominor]

one of my main reasons for staying with the minor box was the amount of problems i have read about with the ford converstions.

Cam's pictures of the ware look the same as the clutch from my golf gti after 120,000 miles of racing and heavy towing!

Is it possible that the clutch is not fully releasing and causing premature wear?

[rayofleamington]

Is it possible that the clutch is not fully releasing and causing premature wear?

certain transmission systems keep the clutch / release system permanently loaded (ie permanently under pressure!) to allow faster openeing. The fingers and release bearing still last the life of the car. However this uses a central slave cylinder (a big slave in the bell housing with a hole in the middle for the input shaft)
That's not so interesting for Morris Minors but proves the point that a roller release bearing will last a long time if it is central.

If the release bearing is off centre, I think this gives a high risk of judder, as the clamp load to the disk will be only at 1 side. Generally that's a very bad idea and also gives a side effect of large side loads to the input shaft. Might be a good idea to check the spigot bush and renew if it has been affected!! If it wears heavily then bigger stresses are passed to the input shaft primary bearing

[Alastair]

I had an identical problem to Cam's with my Ford clutch conversion, only it wore through most of the fingers in about 15,000 miles which was rather depressing. I never really got to the bottom of what was causing it but assumed it was the slave cylinder not releasing properly and keeping the thrust in contact with the diaphragm. From the discussion here though I'm wondering whether the thrust was out of alignment because, as I say, not all the fingers wore through. Unfortunately I binned the offending parts so I can't refer back. I've since gone back to the Morris clutch with a roller release bearing and it seems fine and perfectly capable of coping with the 1275 motor... but then I may be tempting fate as we're off to Ireland for a fortnight next week!

[Cam]

Might be a good idea to check the spigot bush and renew if it has been affected!! If it wears heavily then bigger stresses are passed to the input shaft primary bearing

spigot bush? do you mean the one inside the end of the crank? If so then that's getting replaced as it has broken up. Also the seal on the gearbox input shaft is being replaced as I am changing the front plate to one with the release bearing guide sleeve on.

Alastair,
Did you suffer with bad clutch judder in 1st and reverse?

I never really got to the bottom of what was causing it but assumed it was the slave cylinder not releasing properly and keeping the thrust in contact with the diaphragm.

According to the Minor Centre it is supposed to run in contact!

I've since gone back to the Morris clutch with a roller release bearing and it seems fine and perfectly capable of coping with the 1275 motor...

Yes, but with my engine I have to use a heavier clutch and I have managed to spin that a couple of times when hoofing it

Here is a better picture of the worn thrust bearing in comparisson to a new one:








Also a side shot of the worn fingers:



And I don't think the rear crank oil seal has gone as there is no oil dribble down the engine backplate, so even if it's slight it can't be serious as I can't spot any:



For more detailed (higher resolution) images please have a look at:

http://potteries.mmoc.org.uk/Members_Ca ... 402_01.jpg
http://potteries.mmoc.org.uk/Members_Ca ... 402_02.jpg
http://potteries.mmoc.org.uk/Members_Ca ... 402_03.jpg
http://potteries.mmoc.org.uk/Members_Ca ... 402_07.jpg
http://potteries.mmoc.org.uk/Members_Ca ... 402_08.jpg
http://potteries.mmoc.org.uk/Members_Ca ... 402_09.jpg

Thanks folks.

[rayofleamington]

crumbs! that release bearing has worn a lot more than I guessed from the 1st pic!
The clutch fingers look useable as it's taken just over half the metal, but you need to sort out the alignment before they wear any more (otherwise it'll be terminal for the clutch cover) - that's the kind of wear you'd expect from a million clutch operations....

I nearly commented earlier - I could tell from the dust on the clutch that your rear crank seal was in good condition!

[Cam]

Ray, the alignment now should not be an issue as I am inserting the guide in place.

I nearly commented earlier - I could tell from the dust on the clutch that your rear crank seal was in good condition!

Excellent!

I have got (bought last week) a new thrust bearing, but which of the following would you recommend:

1. Keep original thrust bearing and diaphragm
2. Fit new thrust bearing and keep old diaphragm
3. Fit new thrust bearing and fit new clutch kit

Obviously 3 should solve the problems but as a professional in the area I thought I would get your expert opinion [/grovel]

[rayofleamington]

I would go for #2

[Alastair]

Cam - no, I didn't notice any clutch judder with mine - I had bee having trouble with the clutch slave which was why I was wondering about the release bearing contacting the diaphragm. The only reason I noticed the problem before it actually failed on the road was because the gearbox (a ''reconditioned'' one) gave up. My release bearing was as bad as yours. After I posted my message last night I was looking at your pictures again and thought the spigot bearing looked less than healthy. I wonder of that could be your problem and whether I should have checked mine in my haste to get the replacement gearbox up and running. Its all good fun, isn't it!

[Cam]

Well, I bit the bullet and bought a new clutch cover and plate (did not really need the plate but heigh ho!) I would rather buy it now rather than have to take the thing apart again soon.

The new diaphragm is slightly different from the old one and is made by QH:



Alastair,
Yes the spigot bearing broke up (probably due to the movement of the gearbox input shaft - as Ray mentioned), but I bought a new one today and it is currently soaking in oil, which is a requirement for these bushes apparently.

I think the mis-alignment of the thrust bearing was the problem and everything else failed because of it.

Its all good fun, isn't it!

Oh yes, hilarious!!!

[Cam]

Bit of an update (for anyone that's interested! ).

The car is back together and made it to and from the Birmingham branch rally last weekend (140 mile round trip).

With the new release bearing moving on the input shaft sleeve there is NO clutch judder!! and the operation is as smooth as a cashmere codpiece!

HOWEVER! The thrust bearing squeals a lot when not under load. I remember the old one doing this but it stopped after a while (I can't remember how long it took).

Anyway the question (that I have asked a few folks) is:

Should the thrust bearing run in contact with the diaphragm or not??

If yes, then I could adjust it so as it runs in closer contact all the time. If no then I could fit a return spring (like the standard Minor one).

At the moment it just rests short of the diaphragm and so I am attributing the squeal to there being more resistance in the bearing itself (due to it being new) than between the bearing face and the diaphragm.

The Minor centre say that it SHOULD run in contact, BUT I have asked a clutch specialist and modern car clutches (with the same bearing type) don't!

So I have had conflicting advice. Opinions folks??

[IslipMinor]

I have a Midget 1380 and Toyota 5-spd in our Minor. As part of a gearbox bearing change I decided to fit a ball thrust bearing for the clutch - bad idea!!

The Minor has done 120,000+ miles with no thrust bearing problems ever, UNTIL fitting the ball bearing. Almost immediately the pedal trembled as the thrust bearing made contact with the clutch fingers and I could not feel any benefit at all.

As part of routine engine overhaul - new rings etc., I found exactly the same problem with excessive finger wear after about 5/6,000 miles. So back to the well proven carbon thrust!

The support for the cluch release arm is poor with the Toyota conversion, and I think this has allowed the pivot bush to wear prematurely. No problems in the last 5,000 miles. The rest of the conversion is absolutely superb.

[IslipMinor]

On the should it/shouldn't it theme, most hydraulic clutches run the thrust bearing in light contact, this is the self-adjustment mechanism. With the Minor mechanical set-up I would not want to have the thrust bearing in contact, even without the return spring, as there is no 'self adjustment' capability and likely premature wear.