Gee - you blokes are a wealth of knowledge. I really appreciate the trouble you've gone to.

I'll have a chance to pull my old one apart tomorrow and see what's inside.

Cheers, Rocky

That list of shapes etc is brilliant, winabbey.

Well, pulled mine apart and the body itself has quite a bit of rust in it so I reckon I'd be best buying a new one. I could possibly try to get the top part ok but I can see rust in the lower section. Minnie has been siting in a shed since 1985 so no wonder it needs replacing. The wheel cyls were rusted solid as was the clutch salve cyl.. Haven't pulled the master cyls apart yet but suspect I'll find the same problems.

Large rubber appears to be straight, not tapered whereas the small one at the bottom is tapered.

Thanks once again for your help.

Rocky

For peace of mind given the time the braking system has been sitting idle a new valve seems sensible to me.

I always buy locally if at all possible, even if it costs a bit more, as it supports local businesses and hence helps them to remain competitive. Here's four local suppliers.

https://minisport.com.au/mini-rear-subframe-brake-bias

https://www.ebay.com.au/itm/CLASSIC-MOR ... 2888505176

https://oz.minisport.com/21a1774-brake- ... -only.html

https://www.minisplus.com.au/classic-mi ... ar-subfame

Minibits in Tasmania say they do a reconditioned unit for $99. You may have to send them yours.

http://www.minibits.com.au/list.php?sub ... &vehicle=1

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Looking at the material winabbey has posted and trying to understand how it works, I think the only vital seal is the larger one where the leading edge closes against the ledge halfway down the bore. So long as that seal edge is not damaged it should work. Even a pitted bore is not an issue as the seal does not act on the bore - fluid has to be able to go around the large seal for the rear brakes to get fluid at lower pressures.
The little seal looks like it's keeping fluid out of the chamber the spring sits in. If that seal leaked and fluid filled the spring space, could there be an hydraulic lock?
These 2 seals do appear to be unique and not like the usual hydraulic seals in the rest of the car.

Technical excellence in this thread - keep it up guys, I love it.

I just pulled apart a crusty and dry 71 clubby one, apart from a little loose rust around the 2 outlet ports it's good inside. Big seal is still soft but has a mark so I have ordered the kit.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

A few people will be interested in your comments re the seal kit suitability.

Well, I decided not to change the big seal, as it had no marks on the seal face when cleaned, is still soft and it has the metal band around it to keep it clear of the bore.
So it's back together with a new small seal and a little rubber grease.
The old small seal was perfect too but I changed it anyway.

These limiting valves seem very durable, the one on my car is now 49 years old and still working fine.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

They do seem to last well. The only reason I replaced the whole unit on the 1966 mini's rebuild was that the metal band had rusted away.
The other questions are: do the replacement seals look like they will work (allowing you have replaced the small seal)? And could the metal band be reused with the new seal (from your comment, I can see what it is there for)?

I didn't want to force the metal band off the seal as it was all good. I have another old valve in the dungeon, so I will pry the band off it and let you know if it will fit the new seal.

The small seal looks identical to the original.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks. Good if it does fit. This issue surfaces occasionally.

I had another valve years ago but it's gone AWOL.
Oh well...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.