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MG Midget and Sprite Technical - 1275 clutch problem

First of all. The clutch was working fine before I started so I doubt if the length of pushrod etc is an issue here.....

Had a leaky master cylinder - old tin can type - that a new seal kit didn't cure so I bought one of the plastic reservoir master cylinders from ebay. Spent forever bleeding the system... tied back the pushrod while bleeding and also allowed the eazibleed to force the pushrod out when I released it.When I'm lying under the car I can see the pushrod moving when the pedal is depressed (by my glamorous helper). When the pedal is down I can't push the slave lever back in at all but can when there is no pressure on the pedal.

The problem is that with the pedal right down the clutch isn't fully disengaging - I'm wondering if this suggests there's something wrong with the slave or it's maybe not the right one - part no AAU2298 which seems to be the one most of the ebay people are selling.

Any suggestions? I'm hoping a NOS tin can master turns up soon.
graeme jackson

It sounds from your description, as if you have ended up with a mis-match between Master and Slave. First thought would be that the "new" master is one of the smaller bore ones so it isn't displacing enough fluid for the slave. But from your car profile it should be the smaller bore one anyway.

Just possibly though, your car was working before with one of the earlier larger bore ones, and a larger bore slave to match, which is now resulting in the mismatch.

Sorry for vagueness on this; I don't trust my memory to quote the sizes and I am not at home to look them up. But someone else will.
Guy W

Graeme - You need to measure how much the slave cylinder pushrod is being displaced, as there are two possibilities:

Too little movement - as you currently envisage, but also

Too much movement - there is not a lot of spare travel available in the 1275 diphragm spring before the release ring on the diaphragm spring contacts the driven plate and pushes it on to the flywheel again. This can be caused, for example, by a master cylinder which is too big or a slave which is too small. It can also happen if the linings are too thick. It is less likely to happen if the cltuch plate is worn.

Measuring the amount of displacement will determine whether it is in the normal range and so which of these two scenarios is happening.
Paul Walbran

I'd also replace your glamorous assistant with one of the pressure bleeding kits - not for everything of course - just bleeding clutch or brakes. I mean to say, having a gunsons easybleed kit in one's arms instead of a beautiful woman would be less than satisfactory...
If all was working fine before the swap, I'd say it can only be a mis-match between the cylinders, what Guy says above makes perfect sense. Might be worth getting a new slave cylinder to suit, then at least you know the whole clutch system is good.
Dominic Excell

Thanks for the replies.

I'm pretty sure the clutch isn't throwing far enough. i've ordered a new seal kit for the original tin can so I'll hopefully get that refitted at the weekend and pray it doesn't start leaking again. if it does then I'll be back.

Dominic. I used an easibleed - the glamorous assistant was just there to try the clutch while I was underneath checking there was some movement.

graeme jackson

This thread was discussed between 12/04/2014 and 14/04/2014

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