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MG MGA - Refurbishing a Master Cylinder

I am thinking about refurbishing my old 1500 master cylinder just for a bit of engineering practice. I do not have it in mind to use the MC again.

I have is a fairly decent lathe (Myford Super 7) with milling attachments and I want to improve my skills.

So, what can you tell me about rebuilding the MC?

There is some very shallow pitting in each cylinder.

1. Can the bores be reamed out slightly and still accept the standard rubber oil seals. If so, what is the maximum diameter I can ream to?

2. If that is a no no, what about sleeving? Are liners available commercially? If not, what are the various measurements I need to know. What is the liner made of?

All good information most welcome.

Steve
Steve Gyles

Steve,

Interesting questions. I don't have an answer but would like to add another question to the discussion. What's the problem with a small amount of pitting in the bore? I imagine a miniscule amount of fluid could get trapped in them and possibly leak around the seal but would not have any effect on braking performance? I would think fluid loss would be almost unnoticeable. Just curious.
Jeff Bennett

Jeff

I can only assume that the small amount of pitting allowed fluid to find the easy escape path when applying pressure. I could not get any pressure to the brakes nor clutch. I put a new MC in and all immediately worked well. 10 years have since passed and the pitting will not have improved.

Steve
Steve Gyles

A small amount of pitting can only reduce the life expectancy of the repair. It will wear the rubber seal.

Steve, If you have access to a press, then why not try to bore and insert your own sleeve, either brass or stainless. The 7/8 ID tube is commonly available for low cost. This would eliminate any question as to the amount of over boring you can get away with.

I had a machinist friend who did his own some 20 years ago.

Chuck
C Schaefer

Thanks Chuck. I have ordered the brass tubing. Will report back in due course on how much of a mess I make of it all!

Steve
Steve Gyles

Steve,

Please do. Did you order the .065" wall tubing? I think I read somewhere that the sleeve should be sealed using some grade of Loctite as it is pressed in place. What grade, I'm not sure of.

Good Luck,

Chuck
C Schaefer

Chuck

Pass on that one. I will measure it when it arrives?

Do I take it that is the correct thickness for this sort of job?

Steve
Steve Gyles

You're asking me?

I am not a machinist. Nor do I play one on TV. I am but an amatuerish, resourceful and imaginative fool who just happens to heve been hooked by the MGA.

I suspect one limiting factor is the amount of interference fit for press fitting. Too narrow a wall and it may collapse during pressing. I would try to freeze the sleeve to make it smaller and press it in quickly before it heats up and in a single continuous motion (do not stop) to prevent it from binding. I suspect that you will have but one shot per cylinder.

I seem to remember the sleeve that White Post put in mine was around 1/16" inch (1.5mm) but that was maybe 10 years ago in a different MGA so I could be easily mistaken.

Maybe some machinist can chime in on this and give us both a lesson.


That is the best I can do at the moment,

Chuck
C Schaefer

If you want an interference fit or to reduce the ptess force, it wuld be better to heat the master, rather than freeze the sleeve. You can get more degrees heat than you can cool!
A Pearse

Why not do both? Tube in the freezer, master cylinder in the oven.

Neil
Neil McGurk

If you have access to it put the sleeve in liquid nitrogen, it will drop in with no pressing required.
J Heisenfeldt

I am not sure my doctor will be impressed if I turn up to his wart clinic with an M/C and sleeves!

Steve
Steve Gyles

And with the nitrogen treatment, you could end up cryogenically treating the brass for a much longer life, smoother pedal feel and better tonal quality!

Just kidding.If you have ever read about the claims for cryogenicaly treating brass musical horns, you know what I am talking about. However they will treat entire engines too.

Chuck
C Schaefer

This thread was discussed between 26/02/2008 and 28/02/2008

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