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MG TD TF 1500 - Brake Master Cylinder thread

I have recently purchased a used master brake cylinder for the TF, and what arrived was not in good condition. In particular, the thread to the hydraulic outlet is badly rusted and needs re-cutting.

Can anyone confirm what tap is required for this job?

I think I am also going to have to clean out the bore which has been left dry for many years, and intend to use 600 wet and dry wrapped round the old plunger lubricated with brake fluid, unless you have better suggestions.

Ian Bowers

You may want to use a 'honing' tool for the bore...not sure if you can keep it 'round' with sandpaper?

Hi Ian,
the thread is British standard fine. (3/8" BSF)
I had success with a cylinder hacksawing a slot along the length of a wooden dowel,slipping fine W&D into it wrapping it around and spinning with a drill. Going a bit oversize wont matter as the replacement
seals available here are a neat fit and tend to slow return any way.

Ray Lee

Ian - As Ray stated the threads are 3/8 BSF and taps are easily obtainable from Uni-Thread or Tracy Tools and I am sure, many other places on your side of the pond. I would caution to be very careful when cleaning out the threads. The sealing surface is at the bottom of the hole, so bottoming out the tap could cause problems getting the brake line to seal properly. The bottom taps that I have gotten from the UK all seem to have a fairly long taper at the end, which I carefully grind off to leave the end or the tap fairly flat, enabling me to run the threads closer to the bottom of the hole. If needed, Uni-Thread also carries a good selection of Re-coil kits. Cheers - Dave
David DuBois


For honing out the cylinder go to your local auto parts store and purchase a brake cylinder hone. They are made for this application and should cost less than 15 GBP.


Gene Gillam


This is such a critical component, is it wise to try and refurbish a used one when new ones are available from Moss and B&G?

Just a thought.

Mike Christie

As always, helpful and informed replies. I will tryto restore the old master cylinder,as a matter of principle, using the ideas above.

Many thanks

Ian Bowers


I fely the same way until my home-restored MC failed. Fortunately I was not going fast and the hand brake worked. I have the kit and parts and will still replace my next one with new or send it out.

Ira Spector (PA)

Remember, the order of parts determined by disassembly is dependent on the knowledge of the last guy who put the Master Cylinder together. A good illustration showing detailed assembly order can save a lot of work. Learned this the hard way.

Safety fast,

Jim Haskins
1953 YD
J. M. Haskins

This thread was discussed between 07/05/2009 and 18/05/2009

MG TD TF 1500 index

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