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Brake Master Cylinder rebuild or replace??

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Grahamhaber Avatar
Grahamhaber Graham Haber
Dingman Township. Pa., NYC,New York, USA   USA
On my annual drive up to Martha's Vineyard from NYC, I notice my heal slipping on my rubber floor mat. It was under the clutch pedal so I thought that was the culprIt. I mopped up the slick spot topped up both reservoirs both down maybe 1/2" and payed close attention to the performance of the clutch and brakes both seemed fine. Once here I pulled the cover and it seems to be the brake master. I have a metal square tank Lockeed with concentric circle mark. The rubber cap seems stiff so I am thinking the rubber parts have aged out but the rest is ok. So do I get the repair kit for ~$5 and install in place, or do I pull it and do it on a bench, do I hone it 3/4" 180grit? Do I buy new Lockeed ~$150 TRW ~$80 Classic Gold ~$60

Thanks for the input,

Graham

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
Most will say R & R but when you have the tin can m/c you have another question to ask yourself first and that is how original do I want it to be. If the answer, like it was for me (in this instance), is very then you try to rebuild. Fortunately I have a pair of those in storage - they are out there but the condition they're in is pertinent.



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell (with extensive bodywork to come). Powered by 'worked' Rover 5 litre V8 (ex TVR Chimera) with efi. T5 box. FC IFS. CC rear attached to Ford FG ute axle. And a whole lot more to yet to come. Stealth is the word.

MGUK Paul Wiley
Watton, Norfolk, UK   GBR
Hi Graham,

Unfortunately the master cylinders have a risk of corrosion inside the bores if the fluid hasn't been changed often enough. The fluid absorbs moisture and that leads to corrosion. It can affect the whole system spoiling the fluid further with fine rust particles as well as damaging the cylinders (master and slaves). So check the bore of the master cylinder very carefully.

It gets very hot and humid where you are (as I understand the local climate) and this won't have helped. If the cylinder is corroded the pitting will be visible. You can try polishing the bore with a wooden dowel wrapped with fine emery paper (wet and dry abrasive) but it isn't a good fix - only in desperation!

If the corrosion is bad, it would be worth checking the slave cylinders also as the same fluid and therefore corrosion might be present there also. After that make sure you change the fluid regularly on a time basis (2-3 years?). It is a cheap and quite simple way of keeping the system free of corrosion. You could change the fluid over to a silicon based one (DOT 5) but that needs the system completely free of the old fluid. In my experience that needs all the components changing at the same time.

A further small tip. The bleed nipples on the slave cylinders are likely to have rusted in making them difficult to remove. Get the correct size socket to fit and use a small tommy bar wrench to apply a balanced force. This removes the nipple with least risk of it breaking off. Tap the end firmly with a copper hammer to break the rust seal before attempting removal, then apply a fine oil or WD40 and leave to soak for an hour. If the nipple is badly corroded, clean the thread with a die or replace. I apply copper filled grease before replacing. This reduces the risk of further corrosion.

When draining the system remove the nipple, dry with some paper towel and regrease. This can be done in a minute allowing a little fluid to drain. As this fluid is going to be replaced with fresh, this is not a problem. If the draining process is done carefully there is no need to bleed the system subsequently. The whole system can be drained and refilled in about an hour if you have a set of ramps, a lift or a pit in which to work. Otherwise all the wheels need to be removed in turn. Start with the wheel furthest from the master cylinder.

Good luck!

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Ex-Calif Avatar
Ex-Calif Gold Member Dan D
Cincinnati, Ohio, USA   USA
1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2012 Jeep Liberty "Tank"
2014 Hyundai Accent "Skate"
I don't know what you do on your car but I would buy the classic gold and replace it. I'd also repalce the rear slaves and the rubber hoses so it is all renewed at one time and then you don't have to think about it for a long time.

If you are "Mr. Originality" and have good skills rebuilding is an option but if you are hesitant at all go with new parts. Brakes are an area that you don't want mistakes.



The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G

Grahamhaber Avatar
Grahamhaber Graham Haber
Dingman Township. Pa., NYC,New York, USA   USA
I love this forum, post just after midnight and my Aussie and Brit comrades respond while I sleep and Dan in Ohio what are you doing an the site at 4:22? but thank you all for your thoughts and advice l smileys with beer

I think my slaves are about four years old, I will check it all flush the fluid maybe try a rebuild if it doesn't look pitted. It is a very slow drip and the brakes don't feel like they have any loss of power. I need a better log book to make sure I change fluid with every other oil change.(<3,000 miles annually)

Boris67MGB Richard Boris
Kings Park. NY 11754, USA   USA
1967 MG MGB
I still have the original metal tank Mk1 brake master in my 67B. Anytime I open the brake system I replace the seals & cups in the master in a car situation; master not removed. I also replace the clutch master cup & seal periodically in the car. I even have changed the cup & seal on the BMC during a road rally. The Mk1 BMC & CMC have common cups & seals; the BMC has a check valve. I usually just buy the BMC kits.

Ex-Calif Avatar
Ex-Calif Gold Member Dan D
Cincinnati, Ohio, USA   USA
1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2012 Jeep Liberty "Tank"
2014 Hyundai Accent "Skate"
LOL - I am an early riser for sure. At the other end 9:30pm is past my bedtime - LOL...

Actually my dad was also and early riser and I asked him once, "Hey dad. You get up every day and are out of the house by 6:30 to work. Why don't you sleep in on the weekends?"

"Every weekday I get up for those bastards. On the weekend I get up for me..."

Didn't understand it much until I hit like 40...



In reply to # 3572077 by Grahamhaber I love this forum, post just after midnight and my Aussie and Brit comrades respond while I sleep and Dan in Ohio what are you doing an the site at 4:22? but thank you all for your thoughts and advice l smileys with beer

I think my slaves are about four years old, I will check it all flush the fluid maybe try a rebuild if it doesn't look pitted. It is a very slow drip and the brakes don't feel like they have any loss of power. I need a better log book to make sure I change fluid with every other oil change.(<3,000 miles annually)



The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G

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tomkatb Avatar
tomkatb Larry Baygents
Dayton, Ohio, USA   USA
1963 MG MGB
I have had bad luck at best in the rebuild game. Nothing for longer than a month except the Spitfire, which was a bear to do. Thus I no long rebuild them.

First step is make sure the parking brake is 100%.

If I replaced the master I would also replace hoses and the brake cylinders. Takes less than 4 hours. The wife does the clips.

I had to make a panic stop yesterday with the 63. Stopped, quick and straight.



L.W.(Larry)Baygents
63B
77 Spit

tvrgeek Avatar
tvrgeek Silver Member Scott S
Bowie, Maryland, USA   USA
1965 MG MGB
Replace. Always replace if you can. If you have to rebuild, start with WhitePost. Some rebuilds are OK, but too many don;t last and failing breaks are bad news.



Cogito ergo sum periculoso

OldDuffer Avatar
OldDuffer Silver Member John S
Eugene, Oregon, USA   USA
1970 MG MGB "Ella B"
1979 MG MGB "Mae B *SOLD*"
I just went through this. In the end, I decided that the money would be well spent on a new TRW replacement MC rather than messing with a rebuild kit. About $90 delivered to my door vs. the cost of a rebuilt kit and the time spent disassembling, cleaning and reassembling just seemed to be the way to go. I'll keep the old one and when I have time, maybe I'll tear it down and learn something about it. In the meantime I'll feel better about the brake system knowing it is brand new. Just my 2 cents.



I was addicted to the hokey pokey but I turned myself around.

RAY 67 TOURER Avatar
RAY 67 TOURER Ray Marloff
Fort Bragg, CA, USA   USA
1967 MG MGB "My Girl"
It all depends on the condition of the bore. However, you won't know what that is until you tear it apart. How much down time are you willing to experience? That's the big question. A single circuit master cylinder, in fair nick, can be rebuilt to like new condition. RAY

Basil Adams Avatar
About 12 miles from Sears Point, CA, USA   USA
If you're into originality, there is a new one with a metal can available - round like the clutch cylinder, not square. A little expensive. The aftermarket one with a plastic reservoir (I've been selling the same one for 10+ years) works great and is economical. I don'r rebuild either - too many things that can be wrong. Basil 707.762.0974 basiladams@yahoo.com



Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains

MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
"If you're into originality, there is a new one with a metal can available - round like the clutch cylinder, not square. A little expensive. "

Yeah pity they didn't come up with the rectangular can too!



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell (with extensive bodywork to come). Powered by 'worked' Rover 5 litre V8 (ex TVR Chimera) with efi. T5 box. FC IFS. CC rear attached to Ford FG ute axle. And a whole lot more to yet to come. Stealth is the word.


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ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, Alberta, Canada   CAN
1971 MG MGB
I used to say rebuild. However, if this is the original master cylinder, then it is now over 50 years old. They were never designed to last that long. I suppose IF the brake fluid had been changed regularly and the bore was in perfect condition, then rebuilding is a good option. But generally, by now, the bores are either pitted or have been honed past their safe limit.



Terry Ingoldsby
terry.ingoldsby@DCExperts.com

Diver648 Gold Member Warren Siringer
Tucson, Arizona, USA   USA
1967 MG MGB
1967 MG MGB GT
1971 MG MGB GT
1974 MG MGB
If you decide to go the TRW route, I have a pair posted very reasonably that I bought and never used. See in buy, sell & trade. Having the originals rebuilt with brass inserts is the best solution but pretty pricey.

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