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MG Midget and Sprite Technical - 1275 Clutch problem

I've just put my 71 midget back on the road after 28 years and for the first 60 miles all has been well. A problem with the clutch is now occuring.

When the car is cold the clutch works fine but after a short while on the road, it does not fully disengage. The pedal goes soft for the first half of its travel and then normal to the floor. Leave the car for a while and the clutch will be fine for a few minutes and then the problem will return.

I have bled the clutch again but with no air visible. The master cylinder pushrod moves the same amount with the clutch working fine and when its not.

I was hoping to get the car to Silverstone this weekend for the first time since 1982 but this now looks doubtful.

Any ideas gratefully received

N Fraser

sounds like an internal leak, either in the master, or the slave cylinder piston seal.

I bet that if you check the slave stroke while it is acting up, it is much less than normal. Then, after a rest, it neutralizes and works normally again, for a while.

The rod at the master cylinder is connected right to the pedal, so it will stroke the same regardless of whether there's a leak in there.

I am wracking my brain, trying to remember how to tell whether the leak is at one or the other. Maybe someone else can remember how.

Norm Kerr

A cause of that symptom can be due to the release ring on the clutch cover not running true.
This causes the release bearing to be tapped back out of contact after a bit of running and then the first part of the movement is used in getting the relear bearing back in contact with the ring on the clutch cover.
This condition can be detected by the presence of a small shimmy when resting your foot on the clutch lightly - enough to get the bearing into light contact with the release ring, but not so far that it starts to operate the diaphragm.

(How did I find this one?
I didn't, my wife did. On the Stelvio pass. I was ahead of her in another Midget which already had a broken clutch cable, and not fancying a U-turn in the narrow roadon the face of the Stelvio with no clutch, didn't want to believer her.
So I bit the bullet and did the U-turn (autotest style) to go back and rescue her. Figured it was that or divorce!)
Paul Walbran

Make sure that the clevis pins and pushrod are fresh, with no major wear. The wear adds up quickly because of the geometry of the system so if you do have a leak in the master or slave cylinder, the problem will be increased by the worn metal parts.

When replacing clevis pins or pushrods, apply a film of grease in order to limit future wear.
Glenn Mallory

Thanks for your responses guys. I have now been under the car ( I have the luxury of a full size pit in my garage) and measured the slave stroke.

The stroke is consistant with or without the problem at 9.0mm but the start and finish position of the stroke are 4.0mm less with the problem. The master and slave where both new when fitted to the car in '93.

Until recently the car has only moved in and out of the garage. Could it be that although the car has not been on the road the seals are ineffective due to their age?
N Fraser

Further update, there is no fluid by passing the seals of the cylinders but when i push the clutch lever by hand there is a heavy vibration when the bearing touches the ring on the diaphram. Could be the same problem as indicated by Paul.
N Fraser

This thread was discussed between 31/05/2010 and 05/06/2010

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