Hmm. must be bare metal packed in cosmoline.

The original finish is not a bright tin look.  I have a Lockheed 1960 brake MS still in the box, metal cap, flat top (not dummy nut).  It is still covered with wax & wrapped in the waxy paper.  The color is the same as most non-rusted units, that is a mottled tin and dark finish with the bright tin welds on the seams.

Do not replate it.

Update. Just grabbed the spring with needle nose an twisted it out. Destroyed the spring but should be able to get a new one.   lastic gismo with rubber cup (check valve)  had frozen and hardened to the housing. Had to pick the old stuff out but finally removed it and polished the inside of the cylinder.  I don't think it has been apart since new. Now I know.

Caspirin.. cat got your tongue?

Thanks all and esp Cranium for the info. It was very helpful.

Thinking of tin plating. Was wondering what original finish is.

If you are going to be painting the masters, be sure to use silicone fluid or you'll be pissed after a week of driving and the paint falls off...

59 Mini Registry calls it a "dummy nut" so I can't be wrong .  See my post above.

 

Sorry for the delay in responding. It's 8 miles to internet here. Cranium, Don't have a good pic but the 1959 Mini Registry describes it very well. The LH pic of under Brake cylinders shows the early cylinder with a removalble nut on the left side of the pic. (RH pic shows later cylinder with conical top). I have the cylinder on the right (of the same LH Pic). They call it the middle cylinder. Quote "It was replaced by the middle master cylinder which has a dummy nut sometime in 1960. " Wrenching flats are machined into outside to similate a nut but are not functional. I'm thinking now that method of spring removal is the same as the later one with conical top. BTW does anyone know the original finish? Thought maybe it was tin plating but not sure. Anybody restore this coating?

http://www.1959miniregister.com/the-1959-mini/mechanical-changes/

BTW, don;t loose those metal caps! I have an extra 1 or 2 which are for sale, but they aren't cheap.

Pretty simple. But you;ll need to pull it apart and measure the bore. I believe the rebuild kits come in different sizes, .065, .070, .075... I gave mine a quick hone, and then lubed the rubber bits, and replaced what came in the kit. plus a quick shot of paint:

I have to rebuild my Brake and Clutch MCs. Both are early OG to the car (1960 Austin Seven) with the metal caps. Without a picture (for now) could you suggest which correct rebuild kits I need and where to order from? Is this a simple rebuild?

 

Thanks in advance.

Well, I "rebuilt" a clutch one, and a brake one. We'll see how it works, once I get the car together!

I think this is what he means by "dummy nut"

They are the early ones.

I didn;t have any issues with the springs sticking in there. I would think a gentle tug would allow it to come out.

Cranium,

You seem to have got the hang of taking them to bits.

Are you any good at re-assembly !

LOL  

I'm not familiar with a "dummy nut". Post a picture.

Yes, disassembly technique is straightforward. However am reluctant to force the spring out. Just grab it with pliers and pull out? If stetches just buy new? Just jerk it out?

everything comes out the bottom. remove the rubber boot, where the piston enters at the bottom, then remove the circlip.

I have an early Brake Master Cylinder the tin canister type with the dummy nut (Clutch MC has removable nut). How does one remove the main spring? I believe it may have a small check valve at its attach point near the dummy nut. I've taken a needle nose and pulled and rotated but am afraid of being too agressive and destroy it. Any insight is appreciated.