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As above, alcohol and boiling water worked well for me.
No need to mangle the outside of the piston.
No need for A pair of externally expanding circlip pliers either, which is nice, because I dont have any, and TBH doubt their ability to shift a really stuck piston, if there is nothing on the internal bore to get a grip on.
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Fill it with water, put it in a plastic bag and leave it in the freezer overnight.
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Fill it with water, put it in a plastic bag and leave it in the freezer overnight.
Wondered about that, but I doubted that the expansion would be sufficient (have you actually done this, or is it theoretical?), especially if the piston isnt extended.
Plus there might be a possibility of distortion of the (alloy in this case) caliper, and it would take longer,
Plus you'd need access to a freezer that you were permitted to put unclean and potentially poisonous things in, you;d need to be comfortable doing so,and you'd need to have the room in the freezer, none of which apply .
So, even if that would work, ethanol and boiling water seem to have the edge,
You'll likely be wanting to clean your caliper anyway
Edited by edlithgow on 21/04/2024 at 02:42
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For completeness,since we are going through alternatives, I should perhaps say that I've been told that a grease gun often has the same threads, so that would be another (rather messy) option, IF you had a grease gun, which I don't, here.in Taiwan
I THINK I probably still have one in The Yook (My 1800 Marina had some grease nipples) but I probably wont again have a brake cylinder to eject there.
Edited by edlithgow on 22/04/2024 at 13:46
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Fill it with water, put it in a plastic bag and leave it in the freezer overnight.
Wondered about that, but I doubted that the expansion would be sufficient (have you actually done this, or is it theoretical?), especially if the piston isn't extended.
I would think the expansion would be more than adequate, but would quite likely have other undesired effects. Liquids are much more controllable.
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Fill it with water, put it in a plastic bag and leave it in the freezer overnight.
Wondered about that, but I doubted that the expansion would be sufficient (have you actually done this, or is it theoretical?), especially if the piston isn't extended.
I would think the expansion would be more than adequate, but would quite likely have other undesired effects. Liquids are much more controllable.
9%, according to these people.
www.lpi.usra.edu/education/explore/ice/activities/.../
IOW, not nearly enough, unless the piston was already most of the way out.
I suppose you could jack it out incrementally,with successive fill-freeze-thaw cycles, which would be rather tedious if starting with 9% of not very much, and would increase the risk of busting something.
Liquid/vapour transitions involve volume changes many orders of magnitude greater (160000% for water at atmospheric pressure, apparently)
van.physics.illinois.edu/ask/listing/1734
and are guaranteed to exert the resulting pressure evenly, limiting the possibility for damage.
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<< Liquid/vapour transitions involve volume changes many orders of magnitude greater (160000% for water at atmospheric pressure, apparently) >>
OK, fine. I assumed you needed serious pressure, which I also assumed might not be enough to solve your problem ?
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<< Liquid/vapour transitions involve volume changes many orders of magnitude greater (160000% for water at atmospheric pressure, apparently) >>
OK, fine. I assumed you needed serious pressure, which I also assumed might not be enough to solve your problem ?
?
As above, the problem was ejecting the brake piston, and the brake piston was ejected, implied by
Pop!
RESULT
And " feeling pleased with myself"( conditionally).
Could have been more explicit, I suppose, but it doesn't really seem very obscure.
I dunno how much pressure was generated by the boiling alcohol, but evidently enough, and, as I said, if it hadn't been enough, an escalation involving the heat from smoking hot oil, chip pan fire stylee (back tae ma roots) probably would have been.
In that setup one could use water instead of ethanol in the caliper, though it might be a bit more dangerous.
Edited by edlithgow on 24/04/2024 at 03:30
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<< I dunno how much pressure was generated by the boiling alcohol, but evidently enough .... >>
Not a great deal more than boiling water, really : water 1 bar at 100° (as we all know) and ethanol 2 bar at 97.5°. Were you using neat alcohol - surely not ? I suppose the v.p. of a mixture would be a little bit higher.
EDIT - I see you were using 75% (wherever that comes from), and I don't think I have any data for that mixture.
Edited by Andrew-T on 24/04/2024 at 09:33
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75% ethanol very widely available here post-covid, as it is the standard hand disinfectant.
Not the case in the UK?
I used to be able to buy 100% (perhaps actually 96%, the azeotrope, dunno) and other useful stuff like acetone, in a local chemist, but that place has closed and I havn't located another supplier, though I havn't tried very hard.
While I'm pleased with this piston-popping technique, Yamaha main dealer did the usual "maybe part of an alien spacecraft?" thing when shown the caliper, so I guess I'll be re-using the corroded pad pin and damaged piston, and improvising the rubber bits, and so it may not turn out to be actually very useful in this case.
On a sort-of-positive note, brake fluid master cylinder lid screws came out surprisingly easily with a fluted screw extractor. Not at all corroded, just the standard mysteriously useless JIS/neoJIS/crosshead problem. Rubber fluid top diaphragm very swollen but doesn't seem to have any holes in it.
Edited by edlithgow on 26/04/2024 at 04:00
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. Rubber fluid top diaphragm very swollen but doesn't seem to have any holes in it.
Hmm...maybe not so good.
Seems to be a possibility that this swelling is due to the use of Silicone brake fluid by a previous owner in the distant past.
The residual brake fluid in the master cylinder has a milky appearance which might also be compatible with the use of Silicone fluid, which wouldn't mix with water contamination or DOT 3 or 4.
Don't remember seeing that with even VERY old and dirty (as in, Taiwanese old-and-dirty) brake fluid in the past.
Contamination with petroleum-based products could also swell rubber components but it would have to be extreme to give visible cloudiness.
Some background here
www.adlersantiqueautos.com/articles/brake1.html
I'll syringe off a sample for possible testing, though I'm not sure yet if that'll be practical or definitive.
If that is whats happened decontamination might be difficult or impossible
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Visible surface droplets when flushing the syringe and reservoir with water tend to support the silicone hypothesis.
Id guess any damage is already done, though, and it wont be made any worse by flushing with DOT3
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