Reuse Old New Brake Fluid

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near Cincinnati, OH
Reusing old, open, partially emptied jugs of brake fluid... Even a decade later...

I'm not talking about a mad layman experiment but rather a fairly easy, controlled environment using... you guessed it, a thermometer.

We know that brake fluid is spec'd as stable, far past the boiling point of water, so there should be no risk to the fluid's properties, boiling off any water in it, if just kept close to the 100C boiling point of water. No?

At this point, again the argument in my mind and surely posed by others is, but why have that risk when brake fluid is inexpensive? Then I wonder, how is that a risk? If someone can't do something this simple, anything else they do to their vehicle seems at least as risky.

Of course new bottles of brake fluid are inexpensive, but is that really environmentally friendly, to discard past open, new fluid with just traces of water because of paranoia about a what-if, worst case scenario exists? I don't think it is worthy of worry that if you keep brake fluid at say 105C till it no longer steams, the water is gone, and it has not come anywhere near its breakdown temperature.

Why the bother? Well I cook a lot, and am a fairly precise person, and it seems quite trivial to me, more of a routine thing than a bother, to dump something into a pot, watch a thermometer, and turn the heat down as it approaches a temp, like 100C in this case. It is about the easiest thing I'd do all day, lol.

So back to the original premise, why waste brake fluid when it is easily made nearly water free with a simple method anyone can do, and frankly replacement brake fluid, while not expensive, is more of a burden to acquire (even if free) than simply heating a pot and keeping it from going much past 100F. That takes about 2 minutes active time to turn a burner on and check it once close to 100F.

Are there not more people recommending to do this because it is not idiot-proof? I have never done it myself, but I got to thinking about wasteful practices in automotive repair and maintenance and this is one of them. It also makes me wonder about alternative packaging for brake fluid.

For example, instead of a rigid container, what if brake fluid came in a squeeze pouch, so when you used the amount you needed, no air was drawn in to displace the void in the now partially empty container volume, no introduction of additional moisture?

For those people not paying attention to details ;) I am not talking about taking used brake fluid and cooking off the water in it and leaving the contaminants behind, only the fluid left in a bulk container to use the next time you need fluid.

Again I think to myself, brake fluid is not expensive, and yet, it's still arguably less trouble for me, as an established cook who pays attention to details, to simply raise a liquid to a temperature than to drive to some auto parts store or order and wait for an online delivery, and then waste the new fluid in a partially used bottle.

I get it, that there are people out there who don't feel capable of doing this, or just want to take a blanket warning position because they're driving on the same roads as someone else who isn't capable of doing it and then has brake failure, but it is starting to seem like madness to me, what I have been doing all these years, discarding perfectly good brake fluid in partially used containers because of the *intelligent* advice of those who don't seem to understand science.

Granted, I just spent enough time typing this, to buy a quart or two of brake fluid. ;) BUT, that doesn't decrease the waste, including the container, and all the associated labor and resources needed to recycle these if you want to take that supposedly environmentally friendly route.

I have no doubt that no one will see the point I'm trying to make. It is not that everyone "should" do this, but rather, it sort of makes no sense not to do this if you are competent in the very basic skills needed to do this simple thing??

I digress back to, "it's not expensive so why"? But then my point is, it's not hard or labor intensive to do it, so why not?

I'm stating this in the context of the home shadetree mechanic, while a pro/garage would use enough volume and the labor rate/savings would not make it worthwhile.
 
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This sounds like the sort of kitchen mechanics Atikovi would participate in. ;)

By this logic, would the underhood temps in the summer ever hit 212'F and help at least the portion in the reservoir? They are designed to get away from engine heat, and cars with headers have been known to boil brake fluid under the hood-- but boil, boil at the 390 degrees or whatever, not the "clean boil" you propose.
 
Doesn't brake fluid like form an azetrope once water combines with it, hence why it still has a "wet boiling point" above water and you don't lose braking if your fluid exceeds 212F.
 
Why not just use one of these? Do they not work?


I have one and have played with it a decent amount. I've never found any in a master cylinder that showed as bad, and I've stuck it in some OLD fluid.
The point was not testing fluid in a vehicle but rather the viability of new fluid in an old, open (previously then closed) container. At the same time, of course a tester for fluid could also check what is in an old container, but this flies against conventional *wisdom* not to use old open containers of new fluid, and if it fails the test, what then, if it is contaminant free except for the water?
 
If you are reasonably good and knowledgeable enough about chemistry and fluids, and retesting for confirmation, why not? Biodiesel became a thing similarly, recycled motor oil is sold by the tens of thousands of gallons as supertech, I plastered trailer planks with used motor oil to further preserve them. You go sir, and publish how to better humanity.
 
i took my chinese brake fluid tester and tested it on a open bottle of brake fluid that was sitting in my garage for 4 years . it was at 1% . granted i don't live in a high humidity area, but i was surprised it was basically still good
 
The point was not testing fluid in a vehicle but rather the viability of new fluid in an old, open (previously then closed) container. At the same time, of course a tester for fluid could also check what is in an old container, but this flies against conventional *wisdom* not to use old open containers of new fluid, and if it fails the test, what then, if it is contaminant free except for the water?
I've used it to test open bottles that I've had around before adding to a vehicle. Some that have been opened, but with the cap on and tight, for several years and I've yet to have one show as bad. I've had fluid that has been in a vehicles master cylinder for 10+ years test fine. I really have to wonder how fluid is getting so much water in it unless there is no cap and it isn't sealed at all.

I don't think it would be worth it to me personally to cook the water out of some old fluid, but I don't see why it wouldn't be possible if you were very ambitious. haha
 
Brake fluid is hydroscopic-it readily absorbs water. Do not ever use an unsealed bottle of brake fluid.
 
One reason for replacing brake fluid at regular intervals is because of the copper that finds its way into the fluid, with moisture being an equal concern.
 
I have a 2.5 yr old opened bottle of DOT3? What I gathered so far is why not boil out what water is in an open bottle.? A consideration if I have another sticky caliper.
 
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