How rusty is too rusty for a master cylinder rebuild? : MGB & GT Forum : The MG Experience

How rusty is too rusty for a master cylinder rebuild? #1
seattlejerry Jerry B Tacoma, WA, USA Sign in to contact 1967 MG MGB 1970 Mercedes-Benz W114 1973 Triumph GT6 MkIII 1979 MG MGB "Kermit"	Topic Creator (OP) Feb 11, 2016 06:10 PM Joined 8 years ago 488 Posts

I have my original master cylinder (the non standard one spec'd for Belgium) and I got a square one from a garage sale.

How rusty is too rusty on this square one? Is it rebuildable?

Any tips on disassembly for the older ones? In the twist video?

Namely how do I get the rest out?

First 3 pics are of the square one. Last 2 are of the Belgium one.

Thanks for all the help folks...I may get this running for the first time in 20 years yet.

Jerry

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Re: How rusty is too rusty for a master cylinder rebuild? #2
RAY 67 TOURER Ray Marloff Fort Bragg, CA, USA Sign in to contact 1967 MG MGB "My Girl"	Feb 11, 2016 06:14 PM Top Contributor Joined 14 years ago 17,490 Posts

All of those pictures tell me that those MCs are beyond repair, unless you get them sleeved. RAY

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Re: How rusty is too rusty for a master cylinder rebuild? #3
seattlejerry Jerry B Tacoma, WA, USA Sign in to contact 1967 MG MGB 1970 Mercedes-Benz W114 1973 Triumph GT6 MkIII 1979 MG MGB "Kermit"	Topic Creator (OP) Feb 11, 2016 06:17 PM Joined 8 years ago 488 Posts

Hi Ray,

What did you do with your 67?

I had hopes that the Belgium one would look decent inside once I figured out how to get it the rest of the way apart.

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Re: How rusty is too rusty for a master cylinder rebuild? #4
ohlord Rob C A tiny Island off the coast of Washington State, N.W., USA Sign in to contact 1957 Land Rover Series I "EYEYIYI" 1957 Land Rover Series I "OVRLND" 1971 MG MGB 1971 MG MGB "Bedouin 2" & more	Feb 11, 2016 06:23 PM Top Contributor Joined 12 years ago 28,878 Posts

Toss it

LNDRVR4X4.COM
Home of Project "INCARN8'

1957 Series 1 Land Rover electric VEHICLE CONVERSION

FIXITUPCHAP.COM
FIXITUPCHAP INCORPORATED

RD3 Radar/ Electronic Warfare Technician
VIETNAM 1969-1972

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Re: How rusty is too rusty for a master cylinder rebuild? #5
melbaver Chris Howells Carrington, NSW, Australia Sign in to contact 1968 MG MGB "Moneypit" 2012 Dodge Journey "Another Shopping Trolley"	Feb 11, 2016 06:24 PM Top Contributor Joined 16 years ago 15,314 Posts

Brakes.......no compromise....new one.

Chris Howells

1968 MGB Purchased already dis-assembled but which is largely back together so I'm a lot less ignorant.

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Re: How rusty is too rusty for a master cylinder rebuild? #6
seattlejerry Jerry B Tacoma, WA, USA Sign in to contact 1967 MG MGB 1970 Mercedes-Benz W114 1973 Triumph GT6 MkIII 1979 MG MGB "Kermit"	Topic Creator (OP) Feb 11, 2016 06:30 PM Joined 8 years ago 488 Posts

That brings up the next question... are you guys with the Mk1's using the plastic reservoir style then?

I also thought about changing to a dual system for safety

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Re: How rusty is too rusty for a master cylinder rebuild? #7
RAY 67 TOURER Ray Marloff Fort Bragg, CA, USA Sign in to contact 1967 MG MGB "My Girl"	Feb 11, 2016 06:30 PM Top Contributor Joined 14 years ago 17,490 Posts

Jerry, having owned the same B for 44 years, my replacing the brake fluid every two years has kept the master cylinder alive. I did install a kit in it, back in the late '80s, but the insides looked like brand new. What you are seeing is the accumulation of moisture in the system. Brake fluid is hydroscopic, which basically means that it absorbs water, and this leads to corrosion if the fluid isn't changed on a regular basis. RAY

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Re: How rusty is too rusty for a master cylinder rebuild? #8
melbaver Chris Howells Carrington, NSW, Australia Sign in to contact 1968 MG MGB "Moneypit" 2012 Dodge Journey "Another Shopping Trolley"	Feb 11, 2016 06:34 PM Top Contributor Joined 16 years ago 15,314 Posts

Sorry, but I'm a pedant

~~Brake fluid is hydroscopic~~, should be: Brake fluid is hygroscopic,

Chris Howells

1968 MGB Purchased already dis-assembled but which is largely back together so I'm a lot less ignorant.

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Re: How rusty is too rusty for a master cylinder rebuild? #9
dickmoritz Dick Moritz Philly 'burbs, PA, USA Sign in to contact	Feb 11, 2016 06:34 PM Top Contributor Joined 14 years ago 26,273 Posts

If originality is important to you, send it off and get it sleeved. I have dealt with White Post Restorations and also Apple Hydraulics and have had good experiences with both. Other folks may have different opinions. YMMV...

Dick

Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Re: How rusty is too rusty for a master cylinder rebuild? #10
RAY 67 TOURER Ray Marloff Fort Bragg, CA, USA Sign in to contact 1967 MG MGB "My Girl"	Feb 11, 2016 06:38 PM Top Contributor Joined 14 years ago 17,490 Posts

Chris, good catch! It's been a long day. RAY

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Re: How rusty is too rusty for a master cylinder rebuild? #11
9146 rick dentel yardley, PA, USA Sign in to contact 1970 Porsche 914 1978 MG MGB 1998 Jeep Cherokee 2001 Jeep Cherokee & more	Feb 11, 2016 06:59 PM Joined 12 years ago 3,966 Posts

X2 on White Post in VA.

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Re: How rusty is too rusty for a master cylinder rebuild? #12
redwoodpecker Woody Reed (Disabled) Disabled Account, Antarctica Sign in to contact	Feb 11, 2016 07:04 PM Joined 8 years ago 339 Posts

The 1st appears pitted too deep to hone out. The 2nd can't tell. Hard to tell any time before you hone. After the first run with the medium grit flex hone, you generally can tell if scratches or pitting is too deep to bother with another pass. Of course it needs to be all apart before any honing. Buying a new one is no guarantee of having a good one. There is some real trash out there being sold. Is new trash better than old trash?

Whatever you do you need to remember you have just worked on the brake hydraulics. When you have it back together it is good advice to take it easy, and inspect for leaks several times after drives, and look for signs of leaks you may not be able to see yet. A single drop of brake fluid outside the system (that you carefully cleaned prior to install) indicates hydraulic failure. If the brakes had been working, compare any new parts to the old. Measurements should be identical between old and new.

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Re: How rusty is too rusty for a master cylinder rebuild? #13
RAY 67 TOURER Ray Marloff Fort Bragg, CA, USA Sign in to contact 1967 MG MGB "My Girl"	Feb 11, 2016 07:11 PM Top Contributor Joined 14 years ago 17,490 Posts

In theory, you can hone out any master cylinder to the point that it is almost perfectly round. However, the new seals will be way too small to seal well enough to keep the brake fluid from bypassing them when put under pressure. This is why having a MC sleeved is a good alternative. It brings the master cylinder's inside diameter back to the original stock dimensions. RAY

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Re: How rusty is too rusty for a master cylinder rebuild? #14
barry s Barry Stoll Alexandria, VA, USA Sign in to contact 1972 MG MGB GT 1974 MG MGB 1976 Triumph TR6 1980 MG MGB	Feb 11, 2016 07:30 PM Top Contributor Joined 14 years ago 7,461 Posts

As Woody said its the pitting that determines reusability, not how rusty. Of course, the longer the rust is in place the more pitted the surface.

I had wheel cylinders sleeved by Apple and was quite pleased.

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Re: How rusty is too rusty for a master cylinder rebuild? #15
Andy Preston CA, USA Sign in to contact 1955 MG TF 1500 1960 MG MGA 1600 Coupe 1967 MG MGB 1969 Jaguar E-Type Coupe & more	Feb 11, 2016 07:51 PM Joined 14 years ago 237 Posts

Your life depends on your brakes. Buy a new one and don't even think about rebuilding them. A one day hospital bill will be 1000X the cost of a new MC.

Andy

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