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How to disassemble a master cylinder

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mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
I'm hoping to rebuild and reuse my master cylinders. They cleaned up nicely and I was able to get retaining clips, washers and rods out, but the innards will not budge. I tried blowing 90 psi of compressed air into either opening with no luck. Does anyone have any suggestion on how to proceed or should I just go the reproduction route and save myself a lot of hassle?



Michael Coomey
Paxton, MA

'57 TR3

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TuRtle5 Avatar
TuRtle5 Kevin Kelly
Absecon, NJ, USA   USA
1949 Triumph 2000 Roadster "Coral Mistress"
1959 Triumph TR3A "Drandulet"
1962 Triumph Vitesse "Ohtoseethelightofday"
1968 Triumph TR250    & more
Mike- I strike them down hard on a piece of wood. If they don't move, I push the cylinder in a little and hone or sand the cylinder with fine paper, lubricate with oil and strike the wood again.

Kevin

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Success!!! Thanks, Kevin.

The key was to push it in first and lightly hone the cylinder. After that, the compressed air shot it out no problem.



Michael Coomey
Paxton, MA

'57 TR3

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Fictioneer Avatar
Fictioneer Doug Hirt
Colorado Springs, CO, USA   USA
In reply to # 1492073 by mcoomey
The key was to push it in first and lightly hone the cylinder.

Hi Michael,

I'm going to be tackling this soon with my TR4A's master cylinders and am unsure of the whole honing process -- what type of hone to buy, how to determine when honing is necessary, and how aggressive it ought to be. Any tips?

Doug



"Mr. Filby, do you think he'll ever return?"
"One cannot choose but wonder. You see . . . he has all the time in the world!"

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Doug,

In my case, it turned out that the cylinder was in great shape but there was some built up oxidation/corrosion around the lip that was preventing the removal of the internal parts. I just used an old brake cylinder hone that I happened to have to smooth that out so that the seals could be removed. I didn't actually hone the complete cylinder. In fact, I could have just as easily used some 600 grit sandpaper around my finger.

In your case I think it would depend upon what you find when you take it apart. Since you're planning to rebuild the cylinders I assume that you're having an issue with their functioning. If you're leaking fluid it could be that just replacing the seals would fix the problem. I would only use the hone if you saw scoring of the cylinder walls.



Michael Coomey
Paxton, MA

'57 TR3

Fictioneer Avatar
Fictioneer Doug Hirt
Colorado Springs, CO, USA   USA
Actually, I think my cylinders are pretty good. It's only because I'm completely disassembling the car to replace panels and repaint, and separating body from chassis frame to clean, paint, and re-enforce, that I thought rebuilding the MCs was in order. But the fact is, even thought this car hasn't been driven in almost 10 years, when I opened the MC caps, the reservoirs were still filled to the brim with fluid. So, maybe I shouldn't do anything but clean up the outsides???? Or, replace the seals as a preventative because the car is 50 years old???



"Mr. Filby, do you think he'll ever return?"
"One cannot choose but wonder. You see . . . he has all the time in the world!"

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
I would absolutely inspect the bores and replace the seals. Losing your brakes is no fun at all! And old brake fluid turns corrosive over time, whether the car is driven or not. Even with the MC seal still holding, the bore could be corroded.





Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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TuRtle5 Avatar
TuRtle5 Kevin Kelly
Absecon, NJ, USA   USA
1949 Triumph 2000 Roadster "Coral Mistress"
1959 Triumph TR3A "Drandulet"
1962 Triumph Vitesse "Ohtoseethelightofday"
1968 Triumph TR250    & more
I've been using silicone fluid for 20 years now and you'll never see that corrosion again. Many people say things against it- but it's in all of my old stuff and I have no problems.

-K

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1492097 by TuRtle5 I've been using silicone fluid for 20 years now and you'll never see that corrosion again. Many people say things against it- but it's in all of my old stuff and I have no problems.

-K
Me too! But you'll also never see a stuck piston; which leads me to believe that Doug's car didn't have silicone in it.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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TuRtle5 Avatar
TuRtle5 Kevin Kelly
Absecon, NJ, USA   USA
1949 Triumph 2000 Roadster "Coral Mistress"
1959 Triumph TR3A "Drandulet"
1962 Triumph Vitesse "Ohtoseethelightofday"
1968 Triumph TR250    & more
Randall- quite right

Jacad Avatar
Jacad Gold Member Barry Shefner
Montreal, QC, Canada   CAN
1959 Triumph TR3A "Loose Wheels"
1976 Triumph TR6 "The Tweetster"
and not to forget that if you intend to go to dot 5 silicone, you need to change ALL brake seals so dismantling and reassembling all cylinders with new seals and cleaning out all brake/clutch lines is a must!



Barry
59 TR3A 0TS57675LO - "Loose Wheels"
76 TR6 CF54266U - "The Tweetster"
Website: Triumph TR2-TR3-TR4 www.trtriumph.com/ (sorry for not keeping it current for the past couple of years)

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Forgive my ignorance here, but I haven't studied up on hydraulic fluids. I'm in the midst of a complete off-frame restoration and have replaced/rebuilt all things hydraulic with new lines, seals, o-rings, etc. but have not added any fluid yet. So what are my options? Am I OK to go ahead and use this DOT 5 silicone or does it require special seals that I likely did not use?



Michael Coomey
Paxton, MA

'57 TR3

Jacad Avatar
Jacad Gold Member Barry Shefner
Montreal, QC, Canada   CAN
1959 Triumph TR3A "Loose Wheels"
1976 Triumph TR6 "The Tweetster"
Michael,

If you have changed all seals and flushed the lines (or have installed new lines) you can choose which brake fluid you want to use but you cannot mix the two or you risk brake failure. FYI silicone is a bit more "temperamental" than regular dot 3 and it is important that you don't create air bubbles when filling the brake/clutch canister or you will get softness in the pedals. The advantage of silicone is that it does not "eat" paint and the main disadvantage is that for some reason the standard brake pressure switch will likely fail every 2-3 years requiring replacement



Barry
59 TR3A 0TS57675LO - "Loose Wheels"
76 TR6 CF54266U - "The Tweetster"
Website: Triumph TR2-TR3-TR4 www.trtriumph.com/ (sorry for not keeping it current for the past couple of years)

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
There is a good article (IMO) with pros & cons at http://www.buckeyetriumphs.org/technical/Brakes/Fluid/Fluid.htm
It makes reference to two papers that were originally presented to the SAE (Society of Automotive Engineers) back in the 1970s. If you want, you can read those papers here
https://drive.google.com/open?id=0B2H2NJt34OffdnhWS19scjlNUU0

The prohibition against mixing DOT 5 with conventional fluid (DOT 3, 4 or 5.1) is mostly a myth, IMO. I have done it myself several times, and I know others who have done it as well.

What I have seen is that sometimes, old seals and hoses that were previously used with conventional fluid may get soft and fail when exposed to DOT 5. But they also sometimes fail with conventional fluid, so best practice IMO is to replace them any time you're resuscitating a car from a long slumber, no matter what fluid you use.

In addition to not eating paint, DOT 5 does not turn corrosive over time and, at least in my experience, makes brake components last much longer than with conventional fluid. For example, I originally rebuilt my front brake calipers over 30 years ago (on my previous TR3A) and they are still working fine today. When I moved them from the 3A to my current 3 (back in 2008) even the bleed screws were still working fine.

Conventional fluid absorbs water directly from the air, and becomes corrosive over time. As documented in the Browning article, it actually absorbs not only water, but salt (!) directly through the rubber hoses. DOT 5 doesn't do any of that. For that reason, it does not need to be periodically changed (as conventional fluid does). And you can keep using an open bottle of it. (Since conventional fluid absorbs water directly from the air, you should never use an old, open can of it. Always open a fresh can.)

Some years ago, I watched a white TR4 being unloaded from a trailer at Triumphest in Ventura, CA. Very pretty car, likely a show winner. But, apparently during the trip to TRfest, one of the MCs had let loose and there was brake fluid all down the firewall. Of course the owner washed it off ASAP, but the damage was already done. You could see the paint wrinkling up even as he was washing off the brake fluid.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

mcoomey Avatar
mcoomey Silver Member Michael Coomey
Paxton, MA, USA   USA
Thanks, Barry and Randall. Now I've got more info on brake fluid than I would have guessed existed and I'm sold on the DOT 5 Silicone. It's strange about the brake switch, though. I wonder if anyone is looking into that.



Michael Coomey
Paxton, MA

'57 TR3

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