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MG Midget and Sprite Technical - Brake M/C new seals - stuck!

I've just put new seals into my brake and clutch master cylinders. 1971 Sprite. Both identical in components, only slightly larger on the brake M/C. Clutch is fine. The brake however is now stuck. It's as if the spring hasn't enough force to push the piston back. It pushes it back a short way, but there's loads of travel left where the push rod is loose but the piston isn't coming back.

I am certain I've assembled it correctly, only perhaps with not enough fluid down the bore to start with. I've tried putting fluid in it and using what movement I have to get it to flow, but still no luck. Trouble is, with the piston down the end of the bore I can't dismantle it again to check.


I've tried blowing into the outlet, and removed the push rod and tried sucking on the inlet. No joy.

Ideas?

Ant
Ant Allen

You're having some fun i must say.

Years ago I saw this happen with a friend of mine. I got it free by pushing a fine rod down the outlet and with this I was able to push the piston back towards the pushrod end of the cylinder. Then the fluid was able to lubricate it.
Robert (Bob) Midget Turbo

Ant,

Worth checking you have the correct seal kit - there were two types !

To check look at the tube part behind the bolting flange - its either smooth or has a groove (or ring) going right round. Both cylinders work OK but have differing seal parts - its shown in the Moss book.

As Old and late cylinders were interchangeable often replacements were of the later type (same on MGB's).

If all else fails and you remove the cylinder - a sharp tap onto a wood bench will accereate the piston down the bore and you should be able to tap it out - its just a pain if you have too take it out again i know !

HTH

Richard.
richard boobier

Thanks chaps. I used a coat hanger to push it out again (cleaned it first and did it VERY carefully!). Then lubricated it, compared it with the catalogues, confused myself about which way round it goes, then consulted the diagram in Haynes, then fitted it again and now it appears to work fine. Just hope it doesn't start leaking when I've bled them. It pushes in firmly and then comes out again on the spring now so I stand a chance.

Interestingly, the Moss catalogue doesn't show the main piston piece which is in my cylinder. It is shown clearly in Haynes though so I went with that.

Anyhow thanks again. No doubt I'll be back soon. Four weeks yesterday and it's our wedding using wedding cars sevenoaks car. The engine is in, but not yet run, and the rad and front panel are almost on now too. No wings yet.

Ant
Ant Allen

This thread was discussed on 22/03/2009

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