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MG Midget and Sprite Technical - Can I buy a new tin can brake mast cyl somewhere?

Hi all, my original tin can brake master cylinder has sprung a leak out the end where pushrod is. I put a kit through it but because it was a couple of years ago so I can't remember the bore condition but think it was ok then. I've only just put fluid in and noticed the leak. So what are my options? Can I buy a new one the same? If not can I get a sleeve put in it. i.e. is there enough wall thickness to do this? If I have to get a new one with a plastic reservoir which ones are the best quality? Thanks
Greg H

i don't think you can get them new. used ones crop up on fleabay from time to time - that's where i got mine for a decent price.
graeme jackson

There are sometimes some NOS items on fleabay, although I do seem to remember some specialists advertising them.
Dave O'Neill2

You can get it sleeved no problem. A common course here for people wanting to retain the tin can and full refurbish. Not cheap though as the can has to be removed to drill the hole though from reservoir to cylinder, and the re-fitted.
Paul Walbran

You could try Coastings
Dave O'Neill2

Paul I did wonder about that as it's obviuosly not removable like a bolt on plastic tank. I thought it may be possible to predrill the sleeve before pressing it in.

Thanks for the link Dave. I've sent them an enquiry so we'll see what they say.
Greg H

Greg have you got anyone locally who does sleeving? If not, there are a couple here who do that might be worth following up.
Paul Walbran

Moss sell them. Item 44 for a type 1, with a groove on the body.

Anybody know what the difference is between the groove, and no groove versions is?
Lawrence Slater

I suspect one version has a groove on the body, the other doesn't. But I may be wrong ;-)

(On Mini tin can cylinders the grooved type has two ring-type seals which fit over the piston, the ungrooved type has one ring-type seal and one cup seal.


Paul I could probably find someone locally to sleeve it if I had too but as you say might cost a bit.

Good find lawrence and that's a very good question about the difference between the two. Mine has no groove in it so the early unavailable type. If the later type looks the same and works the same then that would be fine. So does anyone know if that's the case? If so then I'm sorted.
Greg H

From Growlers link.

"Early Minis were fitted with tin tank master cylinders for both brake and clutch. These were generally fitted to all Minis until 1969. There were different variations of tin tank master cylinders, which are identified by whether they have a groove around the base of the master cylinder. The type without the groove ('no groove' type) has different seals internally - one o-ring style seal and a cup seal. The groove type has two o-ring style seals. Therefore it is important to identify your master cylinder before purchasing a rebuild kit so that the seals are correct.

The rules for groove versus no-groove master cylinders is applicable for both brake and clutch tin tank master cylinders. Do note however that the internal bore size differs for brake and clutch - tin tank brake master cylinders are 0.7" bore diameter and clutch is 0.75". It is possible to swap a brake and clutch master cylinder as they are identical internally other than a one-way valve fitted to the brake master cylinder. Therefore it is recommended to measure the bore size of your master cylinder. Sometimes the bore size is stamped on the cup seal on no-groove type master cylinders."

Seems to suggest that the groove type is just an improvement on the earlier non-groove type, and has the same internal bore size.

So I reckon you can fit the later grooved type.

I reckon Moss ought to be able to confirm that.

What's the worst that can happen anyway? LOL.
Lawrence Slater

Worst than can happen? It's functional and would worrk well but actually a new equivalent and turns up with a plastic tank. :( If so it wouldn't be lonely because it can go in the box with all my other new unwanted parts.

I'll find out what the story is between them.
Greg H

You can have a boot(box) sale Greg. :)

But I wondered that. The pic indicates a tin can, but you could be right, it may be a plastic job.

Worth a phone call to find out. I'll call them and ask.
Lawrence Slater

Yup, it's a plastic reservoir.

I was told it's now an EU ruling that dealers can no longer supply the original tin can version. Sales chap wasn't sure why, but it's a couple of years old.

Time to get out of the bloody EU and their petty interference.
Lawrence Slater

The original Mini ones with Lockheed stamped on them are still available - I've just fitted one. But would it not be simpler just to change the cans over?

F Pollock

One of the difrences is the seal kits. One set have holes in them to fit over the pushrod, whilst the other don't and have solid seals - guess how I know.
Jeremy 3

Just re-reading your original post... would it not be worth taking it apart and looking at the bore?

You may get away with honing it and fitting a new seal kit.
Dave O'Neill2

Well I contacted MGOC who told me they stock the later unit which was a tin can but about 8 years ago both the MGB's and midgets chnaged over to plastic.

I'll pull it apart and have a look but I did put a new kit in it when I cleaned it up. Stay tuned.....
Greg H

Here in the States this guy:
removes the cans and resleeves the cylinders.

I'd guess that someone in Australia offers a similar service.
Trevor Jessie

Well pulled it apart and the bore is very nice. There's some minor wear marks at the end but this is where the end of the piston contacts not the seal which runs is further up. The seal looks as new too, as it should because it is new. So not sure why it's leaking. I've decided to buy a new master cylinder (ugly plastic tank one)and I'll get a another seal kit to try as well as they're on a few pounds.

Greg H


Greg H

the piston

Greg H

Did you hone it when replacing the rubber bits?
Trevor Jessie

No because I couldn't find my little hone so I just gave it a light scuff with fine 'wet and dry' paper.
Greg H

This thread was discussed between 13/08/2012 and 21/08/2012

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