Clutch mystery

NickDunning

NickDunning

Active Member
Folks
My ex-factory red 1966 2000 had a slipping clutch - only really noticeable when at 30mph plus in fourth gear and applying some revs.

Today my good friend Duncan has popped the clutch - results below. There is a band of wear/heat friction about 5mm in from the inner edge about 5mm thick. Does anyone have any idea why this has happened - there is plenty of meat on the clutch - which explains why it doesn't slip at low speed.

This is a real head scratcher. Could it be the input shaft? would the release bearing do this?

Help!

Thanks
Nick

clutch1.jpg


clutch2.jpg
 
I had this happen to me on a Dolomite Sprint ??? Whilst doing other jobs on it,I decided to investigate!
After scratching my head and examining the parts,the only thing I could summise was, that on depressing the clutch,
some of the fingers on the pressure plate were weaker than the others and still gripped the friction plate for a while,!! The same when releasing it,part of the pressure plate touched the f/plate first,this led to uneven but minimal wear causing a hot high spot!
The clutch bearing fork was not bent,so the bearing pressure was even. if your fork is out of line it will upset the pressure the bearing puts on the fingers,causing uneven release and grip.
Just one of the joys of classic cars!!
Had the car stood for a while? was the clutch siezed but released after the usual methods were employed??
It could of caused a small rust spot on the plates that has got hot thru use!!
 
how old was the clutch as there is some very bad recon units being sold as new out there at the moment
 
pilkie 0 said:
I had this happen to me on a Dolomite Sprint ??? Whilst doing other jobs on it,I decided to investigate!
After scratching my head and examining the parts,the only thing I could summise was, that on depressing the clutch,
some of the fingers on the pressure plate were weaker than the others and still gripped the friction plate for a while,!! The same when releasing it,part of the pressure plate touched the f/plate first,this led to uneven but minimal wear causing a hot high spot!
The clutch bearing fork was not bent,so the bearing pressure was even. if your fork is out of line it will upset the pressure the bearing puts on the fingers,causing uneven release and grip.
Just one of the joys of classic cars!!
Had the car stood for a while? was the clutch siezed but released after the usual methods were employed??
It could of caused a small rust spot on the plates that has got hot thru use!!
Click to expand...
Dave
This is one we thought of after I posted this. The clutch is ancient and the fingers could well be the problem. The car has done 115k so I would doubt it's the original clutch, but it's been there a very long time.

It's a strange one though.

The car has been on the road for most of it's life, it has sackloads of history. But it has been 41 years so there's always a chance the clutch has been seized at some point.
Thanks
Nick
 
jay said:
how old was the clutch as there is some very bad recon units being sold as new out there at the moment
Click to expand...
Not sure Jay, but I would reckon 1980's. Been on there a very long time.
Cheers
Nick
 
The surface of the pressure plate looks very elderly indeed. Not sure if the picture is giving a false impression but if I saw a plate like that I'd expect clutch judder at least.

Chris
 
As a matter of course the spigot bearing should be checked whenever a clutch is replaced, along with its running clearance. Same goes for the free operation of the release bearing in its housing, although they are rarely known to fail by virtue of their design it does happen.
But looking at that pressure plate with the heat marks only around that narrow band indicates that that is the only area that is actually clamping the centre plate properly, and that is sufficient until the load increases, and it starts slipping and all the heat is transferred through that small area.
A look at the other side of the pressure plate will give more clues, but I'd be fairly confident that a decent quality new centre and pressure plate will cure the problem.
 
harveyp6 said:
As a matter of course the spigot bearing should be checked whenever a clutch is replaced, along with its running clearance. Same goes for the free operation of the release bearing in its housing, although they are rarely known to fail by virtue of their design it does happen.
But looking at that pressure plate with the heat marks only around that narrow band indicates that that is the only area that is actually clamping the centre plate properly, and that is sufficient until the load increases, and it starts slipping and all the heat is transferred through that small area.
A look at the other side of the pressure plate will give more clues, but I'd be fairly confident that a decent quality new centre and pressure plate will cure the problem.
Click to expand...
Thanks Harvey
Clutch going in in the next day or two, so hopefully an improvement...

Thanks
Nick
 
NickDunning said:
harveyp6 said:
As a matter of course the spigot bearing should be checked whenever a clutch is replaced, along with its running clearance. Same goes for the free operation of the release bearing in its housing, although they are rarely known to fail by virtue of their design it does happen.
But looking at that pressure plate with the heat marks only around that narrow band indicates that that is the only area that is actually clamping the centre plate properly, and that is sufficient until the load increases, and it starts slipping and all the heat is transferred through that small area.
A look at the other side of the pressure plate will give more clues, but I'd be fairly confident that a decent quality new centre and pressure plate will cure the problem.
Click to expand...
Thanks Harvey
Clutch going in in the next day or two, so hopefully an improvement...

Thanks
Nick
Click to expand...
Well the new clutch is in, and the gearbox is now from a 1973 2000TC with the remote gearchange, freshly fettled.

Talk about a difference...it feels utterly superb. Just need to get the remaining air out of the Dunlop brakes (just had a new brake flexi - the one with the banjo end - made up by Past Parts) and she will be appearing on an eBay near you!

Cheers
Nick
 
NickDunning said:
harveyp6 said:
As a matter of course the spigot bearing should be checked whenever a clutch is replaced, along with its running clearance. Same goes for the free operation of the release bearing in its housing, although they are rarely known to fail by virtue of their design it does happen.
But looking at that pressure plate with the heat marks only around that narrow band indicates that that is the only area that is actually clamping the centre plate properly, and that is sufficient until the load increases, and it starts slipping and all the heat is transferred through that small area.
A look at the other side of the pressure plate will give more clues, but I'd be fairly confident that a decent quality new centre and pressure plate will cure the problem.
Click to expand...
Thanks Harvey
Clutch going in in the next day or two, so hopefully an improvement...

Thanks
Nick
Click to expand...
I think the fault causing the clutch slip under load was Dave's theory - the clutch was so old and weak the fins were causing it to slip. Feels a hell of a lot better now.
 
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