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MG MGB Technical - 63 B Master Cylinder Leak

I've just noticed that the master cylinder on my '63 B has developed a slight leak on the bottom edge-fold of the reservoir. Now here's the thing, the original metal-reservoir version of the MC is no longer available new. I was wondering if I could just solder the bottom lip to get rid of the leak, has anyone tried this? Or are there any pitfalls in doing this? The MC is good condition apart from this, no rust and good seals. The annoying thing is I just replaced the hoses and fluid last weekend... sods law!
Tony Lyons

Tony - Soldering the M/C reservoir is an iffy situation. First you have to make sure that everything is absolutely clean of all brake fluid, particularly if you have used silicone fluid. The next problem is that there is no rust or corrosion on the metal that you ar egoing to solder. I would suspect that there is rust on the inside of the can and that is the reason that it has started to leak. That said, I would probably give it a shot with solder, you have nothing to loose. If that fails, I will bet that there are a number of old M/C around in peoples stashes that would be available to a fellow enthusiast ( I may have one myself, I'll have to chack. Good luck - Dave
David DuBois

Tony - I forgot to add, DO NOT use acid core solder or acid flux when soldering the can. Get some good organic, non corrosive flux to use. Cheers - Dave
David DuBois

Hi, Tony - Very good info from Dave, as usual, but I personally have no problem with acid-core solder for a project such as this. If you've got the metal shiny clean beforehand, with scrapers and wire brushing, then common electronics rosin-core solder will work fine, but the acid-core may give you a bit of a safety margin.

The main problem with acid core is that it is messy, and spatters quite a bit. Then, there's the cleanup issues. You must be ABSOLUTELY sure to clean the joint well after doing the job, and a wash with some baking soda solution to fully neutralize the acid would be a good idea.

I just removed the can from a Clutch M/C, and it took quite a bit of heat to keep the solder melted, so a very large soldering iron, or a propane torch is essential to get the metal fully tinned. Obviously, the internals of the cylinder must be removed, the can flushed out with hot, soapy water, and then dried thoroughly before you attempt the repair.

On another note, has anyone powder-coated the outside of a brake cylinder? I'm wondering how powder-coating holds up under DOT-3 or DOT-4 spills. Does it flake off like most paints? I'll bet this would be an easy place to brighten up the engine bay, or use silver-gray for an original appearance.

Cheers, y'all - - Alec
Alec Darnall

Thanks Dave and Alec for your help, I'll give it a go with the solder at the weekend.

All the best, Tony
Tony Lyons

Tony, you'll stand a chance if you mechanically clean the area to bright steel first and use a flux such as Bakers Fluid aka killed spirits. Corrosion and brake fluid are two problems but the other is the plating which may be cadmium or zinc and will need that flux. One of the large gas heated irons would be the tool. The real problem may be fluid in the folded join. Good luck. Rich.


It looks like they're still available, at least from Moss. MGOC may have them also.

Paul K

Thanks for the info Paul, I know Moss Europe only sell the plastic reservoir versions. I'll drop Moss Motors a line, although it does state "Lockheed Replacement" on their website, they may have a different supplier in the US. I'll give the MGOC a call, parts aren't listed on their website. I've already tried most of the other larger dealers in Europe.

In the meantime I have removed and soldered the original MC. There were no visible gaps so I guess one of the reservoir joints was porous. If that doesn't do the job I'll have to go for the replacement with a plastic reservoir.
Tony Lyons

hello Tony, it seems that this guy may have some...this is a quote from the 'moss bashing' thread

" I order from Chris Roop in Oregon. Just bought a master cylinder for my 67 from Chris and it is the original style with the metal can. He had some NOS in stock."

..Sorry I don't have any more info...but you may just shop around instead of trying to fix yours...
Jeremy RG

hello again tony,
I should add that this other thread may be referring to a clutch master and not the brake, but I still think someone will have some laying around.
Jeremy RG

If you started with one copy of the NAMGBR's "MGB Diver" you will have enough ads and business cards that someone will have or point you on to who has. Another reason to join!

In any case, get one now and refurbish it. They are not common to many cars and a repair is questionable--espec if you're using LMA, dot 4 or 3 paint eating fluid.

Just my 2 bits

Paul Hanley

I just got one from Chris Roop. I am not sure, but he may have another one in stock.
Jim Lema

Thanks for all the info, but after soldering the joints, the problem seems to be solved. I will be be on the lookout for new old stock just in case. As to the clutch cylinder that is still available will a metal reservoir!
Tony Lyons

This thread was discussed between 19/05/2005 and 30/05/2005

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