Open brake fluid container

[The Disapproving Brit]

I changed my brake fluid at the weekend, and now I have most of a bottle of DOT4 left. From what I gather, brake fluid is hydroscopic, and shouldn't be stored once opened. Is that the kind of advice that should actually be followed, or is it bollocks?

If it's now unusable as brake fluid, does it have any other use other than the obvious paintwork based revenge?
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Current Bikes: 1983 Honda VF400FD / 2003 Honda VT750 Shadow
Bike Test Passed 18/03/09, Car Test Passed 14/05/13

[Hetzer]

It's bollocks. I've used stuff in half-empty cans/bottles I've had for years and it's worked fine. Make sure the lid's done up nice and tight and keep it somewhere cool.
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"There's the horizon! Ride hard, ride fast and cut down all who stand in your way!"

[Raffles]

If it makes you feel better then you could always decant it into a smaller container.
Personally, I'm with Hetzer and struggle to accept that brake fluid significantly deteriorates due to exposure to air*

*Awaits incoming flak from more knowledgeble people that will disagree with me and point out that the fluid can boil and cause brake failure when contaminated with water and everyone's likely to die as a result.
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A good loser will always be a loser.

[totalllama82]

Have to admit, i've used old stuff on cars before and found no real difference.
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Gone: Haotian HT125-8 / Yamaha YZF 600R Thundercat / Kawasaki ZX9R C2
Current: Kawasaki ZZR 1400 A7F

[Kickstart]

Hi

It does absorb fluid pretty rapidly. But I would still reuse some from a bottle which had been securely resealed fairly recently. But I would be dubious about a bottle that had been opened and closed a few times over 6 months.

Found this that might interest you:-

https://www.iwsti.com/forums/gd-braking/44252-brake-fluid-101-a.html

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[bikenut]

yes it is hygroscoptic......and absorbs water........which lowers boiling point and causes corrosion...........you change the fluid once a year or every other like on a merc??

[neatbik]

[The Disapproving Brit]

Cheers guys. For it's next full change it'll be a new jar again, but I only had time to bleed the front on my day off. I still want to bleed the rear and clutch, but won't get chance for a couple of weeks, so wanted to be sure it's still going to be fine to use the same fluid.

On a related note - I know brake fluid eats paint. Does it render the surface unpaintable in future?
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Current Bikes: 1983 Honda VF400FD / 2003 Honda VT750 Shadow
Bike Test Passed 18/03/09, Car Test Passed 14/05/13

[Hetzer]