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How long would you think brake fluid would last once the seal has been broken and it is kept in its original container on a shelf?
 

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I flush my 2 bikes every year, a little excessive??, maybe, but better safe than sorry.
I would not go more than a year, since it does absorb moisture.
So, in a dry place or environment 1 year, but it's not that expensive, so when in doubt, throw it out.
 

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It doesn't matter what I'm thinking about the opened container fluid, as one can be dead wrong.
1. The proper way would be measuring the boiling point, if that's good (for it's class, eg. DOT4 is within DOT4 specs), then fluid is okay. (I don't have tool for this).
2. No tool, so wild guessing, that if the colour of the fluid is about the original (in my experience very pale/light yellow), then assuming that the fluid is okay. Which is can't be a problem if one doesn't rely on hard braking, then even if the colour seems good, but in reality the fluid is bad (wet, with lower boiling point) can't generate problems. On the other hand, on a trackday one would feel if the fluid weak as the brake lever would come more and more closer to the grip, while it was fine and consistent on the normal road use.
3. Assume, that the opened fluid is fully wet, so it's wet boiling point applies - then the costly race fluids are the best with their super high wet boiling points.

Anyway, I'm defaulting the #2 "method" + I change the fluids on the bike at least 2 years or (most periodic maintenance tables of any brand require this interval), if I have an already opened container, then if I see that it became darker in the reservoir(s), I change it, as it's easy.
I never really had problems because of the fluid, the only bike I had problems (trackday) with the braking was because of one caliper and/or the master cylinder, not the fluid. (and once with race pads which for some unknown reason ceased to work at one braking point @110MPH, so friction lost with regular force on the lever, and with very strong grip it locked the front wheel - almost crashed onto the runoff's wall - then it never happened with the very same pads again..)
So the regular DOT 4 with normal (at least in 2 years) change intervals is fine in my experience, even if it comes from an already opened container. If I really care about, then I would open the new/already opened fluid on a least humid day, and careful about that the seal of the container.
 

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How long would you think brake fluid would last once the seal has been broken and it is kept in its original container on a shelf?
Just imo: If it's in a sealed container & little has been used it shouldn't have absorbed any more water than it would in a master cylinder. It hasn't been used it should be clean, not contaminated.

I asked the Triumph dealer if the brake fluid change was included in the 2 year/12k mile service. He said "We change it if it looks dirty". I rec'n they charge for it anyway but only change it if it's dirty.
 

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How long would you think brake fluid would last once the seal has been broken and it is kept in its original container on a shelf?
If you put the lid back on tight and didn't have it open for 3 hours while you changed the fluid, then it'll be good for a couple of years at least I reckon. As the guys above said, if the colour is good then generally it's fine to use.
 

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I had one of those moisture testing tools. It was cool, you just put the probe into the brake fluid and then LEDs would light up indicating how much moisture was in the fluid.

It "disappeared" from my toolbox when I quit that job.

This is it:
http://www.cornwelltools.com/webcat/products/OW4598DOT4-%2d-Brake-Fluid-Tester.html


But back to the original question, I wouldn't use anything over a year old. That's why I always buy the little bottles.

When my fluid starts to amber I just go ahead and flush it. I hate looking at nasty brown fluid in my specimen cup.
 

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Seems to me you're pretty safe if through the course bleeding and topping off the res you put the cap on the bottle between. Really, how much moisture can the air in a half of a container of brake fluid hold? And how much of that will drop out of that airspace to contaminate the fluid?
 

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For the small price of a bottle of fluid I would buy new.... The bottles usually tell you to only refresh fluid with an unopened bottle.

It may be ok, but would you bet your life on it?

Sent from my SM-G930F using Tapatalk
 

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After doing a bit of a search, it would seem some, maybe all of us are stuck in a time warp. Brake fluid to Dot 3, 4 & 5.1 are synthetic & do not absorb water. Apparently they can absorb air which would be evident from a spongy brake lever, see link below.

I recently changed the brake fluid in my old Traillie 'cos it looked murky, I used a part used can of Dot 4 that I found on a shelf in my garage, must be 7 or 8 years old. The brakes are fine, not at all spongy. I am quite confident this will not kill me.

Have a read:

http://www.mossmotors.com/SiteGraphics/Pages/brake_fluid/page1.html
 

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After doing a bit of a search, it would seem some, maybe all of us are stuck in a time warp. Brake fluid to Dot 3, 4 & 5.1 are synthetic & do not absorb water. Apparently they can absorb air which would be evident from a spongy brake lever, see link below.
Did you actually read your own link?

Two notable quotes: "Silicone has very high dry and wet boiling points. However, it is more compressible because it will absorb more air than a glycol based fluid" and "DOT 3, 4 and 5.1 fluids are all hygroscopic, meaning they will absorb water out of the atmosphere".
 

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Did you actually read your own link?

Two notable quotes: "Silicone has very high dry and wet boiling points. However, it is more compressible because it will absorb more air than a glycol based fluid" and "DOT 3, 4 and 5.1 fluids are all hygroscopic, meaning they will absorb water out of the atmosphere".
Haha, yes I did! Which part of it did you not understand? It clearly states:

"When it comes to picking a brake fluid for your British sports car, do not consider anything that does not meet FMVSS 116. DOT 3, 4 and 5.1 fluids are all hygroscopic, meaning they will absorb water out of the atmosphere".


And, as I said, it absorbs air which will be felt by the spongy pedal.
 

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Did you actually read your own link?

Two notable quotes: "Silicone has very high dry and wet boiling points. However, it is more compressible because it will absorb more air than a glycol based fluid" and "DOT 3, 4 and 5.1 fluids are all hygroscopic, meaning they will absorb water out of the atmosphere".

Did one of us misread that paragraph also:

The DOT 5 fluids are 70 percent silicone by weight. Only silicone based fluids met the DOT 5 standards when they were created. As a result, DOT 5 has come to be synonymous with “silicone brake fluid.” When glycol brake fluids with borate esters appeared that met DOT 5 specifications, they introduced them as DOT 5.1 to avoid the confusion of having fluids with two very different bases under the same DOT number. Unfortunately, for many people, the “5.1” implies some connection to “DOT 5” and that has created rather than prevented confusion. Think of 5.1 as a glycol based DOT 4 fluid that meets DOT 5 standards. The 5.1 fluids are used primarily in vehicles equipped with ABS brake systems.

Or here:

Unlike glycol based fluids, silicone brake fluid will not absorb water from the atmosphere or act like a paint remover. Silicone has very high dry and wet boiling points. However, it is more compressible because it will absorb more air than a glycol based fluid. The air is in solution, and should not be confused with air bubbles. The dissolved air gives a slightly spongy pedal feel, which most people cannot detect. It makes silicone fluid a poor choice for racing, but it is considered an appropriate choice for a classic car that is not driven daily. Bleeding systems with silicone takes more time and may have to be repeated because it takes time for the air to works its way out.

It is quite a good article, take your time reading it.
 

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Just tested some DOT 5.1 in an container that's approximately 2 years old. No water detected. Same result with that same fluid that's been sitting completely open for about 3 weeks.

However that same fluid that replaced the fluid in my front brake system (24/09/16) tested at 2% water. So 6 months and it is close to needing to be replaced. It has certainly discoloured.
 

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I think the lid design of my front reservoir '15 Speed is a pretty crappy design. It lets moisture in a lot faster than my screw on lid '14 Street Trip. I did notice that all the fluid from the brake lever to the calipers was actually still clear when flushing. It took a while to get to the brown fluid when pumping. Moisture only turned the fluid in the cup brown. They should have used the screw on lid rather than push on with two screws.
 

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Flush mine every year in both bikes.
I buy two bottles, one for each bike.
Keep what's left until next year in case a top off is needed and toss them when it's time to do it again.

The stuff us under $5 US. You ride a Triumph - which isn't the cheapest form of two-wheeled conveyance. Don't worry about trying to wring the last drop of brake fluid out of a bottle.

If you want to know luxury, get a Mighty-Vac or similar brake bleeder. Flushing/bleeding the brake system goes from messy pain in the butt to a 20 minute job for both front and back.
 
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