MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

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 Midget and Sprite Technical - Dragging clutch - all is revealed !

A few days ago, I posted about the problems I was having with the clutch dragging.
Got the engine out tonight and found the release bearing completely worn away (see pic)
- no sign of carbon except for a nice powder coating inside the bell housing !
Quite why this has happened after only 13k miles I'm not sure but I'll certainly replace the original length pushrod, as it had been suggested the longer one I had been using may have contributed to excessive wear.


M J Chapman

Do I get a prize?

Guy
Guy Oneandahalf Sprites

Worth checking the fork arm is not bent as well - often hapens with the extended rod method of sorting a problem.
Ensure all the clevis pins/holes are a good fit also - no slop etc, both at slave and master.

R.
richard boobier

Richard has it right
If the arm is not perfectly held in place the carbon ring can touch the input shaft an this leads to a very rapid disintergation of the ring.
Onno Könemann

Suggest you rebuild or replace slave & master cylinders, esp. the slave. If either is dragging due to dirt/corrosion, it will hold the bearing against the pressure plate enough to eat the bearing.

FRM
FR Millmore

the arms can be re-bushed for pennies, that can help too.
David Smith

Also, not all replacement release bearing are made to the correct dimensions. Some sellers even sell the same bearing for 948, 1098 and 1275 engines, even though they are all different!
Dave O'Neill 2

Dave,

To help ensure the correct bearing is being fitted, what is the key diamention for each of the 3 engine capacities
Doug Plumb

Longer pushrod could be a cause, always fit the original. If it appears too whort, there is a problem somewhere else, most often worn or wrong release bearing though there can be other causes too. Sometimes a longer pushrod has been fitted in an effort to rectify a problems that's due to insufficient travel at the slave cylinder. This makes no difference. Usually the problem is air in hydraulics or wear in the pedal/m'cyl pushrod pivot.

FRM's comments on checking there's no drag from cylinders spot on as usual.

One point to be aware of: 2 or 3 years ago there was a big batch of carbon realease bearings made using a small roll pin in the side to locate the carbon rather than a full interference fit. These invariably failed by 10 000 miles or so, with the carbon stressing around the pin and fracturing. (It cost us a lot in warranty claims as we had sold a quite few before becoming aware of the problem!)

This could be the case here, buit sadly the bearing is so worn that you can't tell. However, when buying a replacement carbon bearing (for any model) check that it doesn't have the pin or you'll have another premature failure.
Paul Walbran

Well, congratulations to all those who subscribed to the bent arm theory (see pic). After straightening, I reckon I've gained about 3/8" linear travel and at least the same again by fitting the new release bearing. I'd already fitted new seals to both master and slave and with a new bush in the release arm, new clevis pin and reverting to the original push rod, I should be "good to go"
On reflection, I think that as Paul suggests above - the root cause of all this bother, was the longer push-rod.
Anyway, all I've got to do now is put it all back together again !!


M J Chapman

Checked with MGOC spares and they list a new release arm as NLA; Moss Manchester had no stock but said they could get one within a week for about 47 quid.
So as another week's hire on the engine crane would have set me back another 60 quid I decided to have a go at straightening this one. Now as I only have a propane torch which would not be hot enough, I decided to get the barbie out (see pic)


M J Chapman

............... and after a bit of caressing with the ol' engineer's hammer - looks a bit better !


M J Chapman

It may now be straight - but is it square? Is the clevis pin in the same alignment as the trust bearing end? It may be an optical illusion but it does not look so in the photo.
Chris H (1970 Midget 1275)

No, it's the camera angle that has distorted it. I used the side of a sledge hammer as an anvil so it was persuaded back into line on a flat face.
Anyway, its back in the bell-housing now and the engine hoist has gone back !
M J Chapman

Good news that it is in OK. I can't believe how bent it was!
Chris H (1970 Midget 1275)

Well, it is a bit too late since you've put it back, but the next time you have it out think about stiffening it to keep it from bending again.

A friend did this by welding a "spine" on the backside of the arm.
David Littlefield

I had to do that on the race car when running a F3 clutch.
Dave O'Neill 2

This thread was discussed between 26/01/2011 and 01/02/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.