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#2129438 - 01/06/11 11:33 AM Do open bottles of brake fluid go bad sitting?
scott37300 Offline


Registered: 11/13/10
Posts: 194
Loc: Wisconsin
Everything I read always says "use brake fluid from a clean, sealed brake fluid container. So if I buy a bottle of brake fluid and only use half of it do I have to throw it away or can I put the cap back on and use the left over sometime later? I understand keeping junk out of it but is there a reason they always say "sealed"? Does it have to do with moisture or something? If so is there a way to store it to prevent moisture?

Thanks

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#2129443 - 01/06/11 11:36 AM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
eljefino Offline


Registered: 06/15/03
Posts: 24657
Loc: ME
It does relate to moisture. But the cap on a bottle of brake fluid is better than the snap cap on most master cylinder reservoirs.

The general rule of thumb is to use brake fluid up within a year.

It turns dark when it gets wet, it should look like ginger ale when it's new.

It's also a "rule" to bleed one's brakes every two years but many people stretch it to a decade then do it when a line rusts out. So you need to look within at how perfect you want it to be.

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#2129452 - 01/06/11 11:45 AM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
Spazdog Online   content


Registered: 09/06/10
Posts: 5606
Loc: Arlington
The thing I do, and I don't know if it helps any or not, is to squeeze the extra air out of the bottle before screwing the cap back on.

So you have this funny deformed squashed brake fluid bottle. But it has almost no air in it that moisture might be in.

I don't keep them too terribly long anyway so I'm not sure if it does a thing for it good or bad.
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#2129478 - 01/06/11 12:18 PM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
Eddie Offline


Registered: 12/07/03
Posts: 6849
Loc: Florida, Cape Coral
I recap and keep for not over a year. One reason I don't buy the large size, but only enought for the anticiped one use.
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#2129515 - 01/06/11 01:03 PM Re: Do open bottles of brake fluid go bad sitting? [Re: eljefino]
CATERHAM Online   content


Registered: 11/18/05
Posts: 9743
Loc: Burlington, Ontario, Canada
Originally Posted By: eljefino

It turns dark when it gets wet, it should look like ginger ale when it's new.


Really, I thought it was heat that turned it dark over time?
It would indeed be handy if it was just the absorption of moisture that turned it dark. That would certainly make it easy to judge the condition of opened bottles of fluid in storage.
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#2129534 - 01/06/11 01:22 PM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
unDummy Offline


Registered: 02/01/03
Posts: 8756
Loc: RI
Its all about the moisture. Why replace wet brake fluid with new wet brake fluid?

Always put the opening date on the bottle with a sharpie or magic marker.

Depending on location, as humidity levels vary, I wouldn't use an open bottle after a year.

Ways of utilizing that open bottle of brake fluid are simple. Simply siphon/refill your reservoir a couple times a year and you won't ever have 'old' brake fluid sitting around. Top off the reservoir as needed.
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#2129665 - 01/06/11 03:09 PM Re: Do open bottles of brake fluid go bad sitting? [Re: unDummy]
scott37300 Offline


Registered: 11/13/10
Posts: 194
Loc: Wisconsin
Makes sense and good idea of using a sharpie

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#2129695 - 01/06/11 03:34 PM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
calvin1 Offline


Registered: 08/08/07
Posts: 779
Loc: Indiana, USA
You could use my defacto method, but I don't really recommend it. It always seems that I'm doing these jobs in the dead of winter so the air that gets into the bottle has almost no moisture in it. I could ship you a jug of dry air for a reasonable price if you want to go this route. laugh

Never mind, I see you're in Wisconsin. Just scoop up some of that dry air next time it gets down below 0.


Seriously, though, I wouldn't worry about a bottle that's been unsealed but tightly capped for less than a year. As someone else pointed out the reservoir in the car is a lot more open than that bottle. The mc reservoir breathes with every push of the pedal.


Edited by calvin1 (01/06/11 03:39 PM)
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#2129749 - 01/06/11 04:17 PM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
sciphi Offline


Registered: 03/24/07
Posts: 8647
Loc: Upstate NY
My rule was 2 weeks, then get new. The DOT3 is cheap enough at $5.xx for a quart to not buy new. It does get expensive when repeatedly flushing the brakes chasing brake problems...
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#2129838 - 01/06/11 05:44 PM Re: Do open bottles of brake fluid go bad sitting? [Re: Spazdog]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
Originally Posted By: Spazdog
The thing I do, and I don't know if it helps any or not, is to squeeze the extra air out of the bottle before screwing the cap back on.

So you have this funny deformed squashed brake fluid bottle. But it has almost no air in it that moisture might be in.

I don't keep them too terribly long anyway so I'm not sure if it does a thing for it good or bad.


This is added insurance, and is a good thing to do. Not a huge life and death difference, but in the right direction.

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#2129846 - 01/06/11 05:48 PM Re: Do open bottles of brake fluid go bad sitting? [Re: unDummy]
Kaie Offline


Registered: 10/31/10
Posts: 259
Loc: Kenmore, WA
Originally Posted By: unDummy
Its all about the moisture. Why replace wet brake fluid with new wet brake fluid?

Always put the opening date on the bottle with a sharpie or magic marker.

Depending on location, as humidity levels vary, I wouldn't use an open bottle after a year.

Ways of utilizing that open bottle of brake fluid are simple. Simply siphon/refill your reservoir a couple times a year and you won't ever have 'old' brake fluid sitting around. Top off the reservoir as needed.



your brake lines are a dead end. Meaning theres no return line. Yes there will be some movement in the fluid. But i highly doubt its enough to do what you are suggesting.

2cents


Edited by Kaie (01/06/11 05:49 PM)

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#2129992 - 01/06/11 07:36 PM Re: Do open bottles of brake fluid go bad sitting? [Re: Kaie]
crinkles Offline


Registered: 05/28/07
Posts: 5493
Loc: Australia
Originally Posted By: Kaie
Originally Posted By: unDummy
Its all about the moisture. Why replace wet brake fluid with new wet brake fluid?

Always put the opening date on the bottle with a sharpie or magic marker.

Depending on location, as humidity levels vary, I wouldn't use an open bottle after a year.

Ways of utilizing that open bottle of brake fluid are simple. Simply siphon/refill your reservoir a couple times a year and you won't ever have 'old' brake fluid sitting around. Top off the reservoir as needed.



your brake lines are a dead end. Meaning theres no return line. Yes there will be some movement in the fluid. But i highly doubt its enough to do what you are suggesting.

2cents


it has to do with concentrations and how the entrained moisture will distribute equally throughout all connected fluid with time. given enough time if your reservoir has a lower concentration of moisture then the hgiher concentration in the lines will equilibrate. this is of course assuming that the water molecules are available to disperse throughout the fluid.

I'd like some physicist or chemist to chime in please because it is a qorthwile question.

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#2130009 - 01/06/11 07:49 PM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
unDummy Offline


Registered: 02/01/03
Posts: 8756
Loc: RI
Kaie, brake lines being a dead end is a mute argument. You haven't been around fluid or mechanics long enough to understand that the fluid moves back/forth and is mixed constantly the hundreds of times you step on the pedal every year. It does NOT need to circulate in a loop to move. And, if you don't believe it, get a straw, some milk, and a glass of water. Suck up milk into the straw, hold the siphon, stick straw in glass of water, draw in and release a few drops of water constantly. Eventually, what is in the milk straw and water glass is the same. You'll figure it out.

Crinkles, the dry fluid will attract moisture from the wet fluid. That should 'even out' the moisture level across the brake fluid. Any dissolved wear in the fluid is also removed. And, you refresh the additive package to help prevent/reduce corrosion.
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#2130098 - 01/06/11 09:03 PM Re: Do open bottles of brake fluid go bad sitting? [Re: unDummy]
scott37300 Offline


Registered: 11/13/10
Posts: 194
Loc: Wisconsin
Originally Posted By: unDummy
Kaie, brake lines being a dead end is a mute argument. You haven't been around fluid or mechanics long enough to understand that the fluid moves back/forth and is mixed constantly the hundreds of times you step on the pedal every year. It does NOT need to circulate in a loop to move. And, if you don't believe it, get a straw, some milk, and a glass of water. Suck up milk into the straw, hold the siphon, stick straw in glass of water, draw in and release a few drops of water constantly. Eventually, what is in the milk straw and water glass is the same. You'll figure it out.

Crinkles, the dry fluid will attract moisture from the wet fluid. That should 'even out' the moisture level across the brake fluid. Any dissolved wear in the fluid is also removed. And, you refresh the additive package to help prevent/reduce corrosion.



I think this is the best description I have heard so far. There was a discusion last week about this and I don't know as much as some here but I didn't really see how the hydralic fluid "mixed". I am going to be doing a couple brake fluid flushes in the next weeks so will have some dirty fluid and will try and use s turkey baster or something to use your example to see what happens.

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#2130622 - 01/07/11 10:17 AM Re: Do open bottles of brake fluid go bad sitting? [Re: scott37300]
sw99 Offline


Registered: 03/22/06
Posts: 1449
Loc: Colorado
I have no problems using stuff that has been sitting for a year or two. Zero problems to date.
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