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Open Brake Fluid #4634825
01/14/18 03:57 PM
01/14/18 03:57 PM
Joined: Feb 2005
Posts: 797
Scituate MA
coopns Offline OP
coopns  Offline OP
Joined: Feb 2005
Posts: 797
Scituate MA
I opened and used brake fluid container (removed fluid and filled).

Can I use again? I thought I remember someone saying it is (yeah, big word of the day...had to look it up) hygroscopic - absorbs moisture but would that apply even with cap on?


Coop
Re: Open Brake Fluid [Re: coopns] #4634849
01/14/18 04:22 PM
01/14/18 04:22 PM
Joined: Nov 2006
Posts: 20,609
MA, Mittelfranken.de
Trav Offline
Trav  Offline
Joined: Nov 2006
Posts: 20,609
MA, Mittelfranken.de
Sure you can, put the cap on tight and keep it in a dry cool place, putting it in a ziplock bag is not a bad idea if its going to be longer than a few months.
Unless you live in a very dry climate like southern CA, NM or AZ, etc I would toss it at the 2 year mark.


ASE L1, Master. Deutsch Meisterbrief.
Re: Open Brake Fluid [Re: coopns] #4634865
01/14/18 04:40 PM
01/14/18 04:40 PM
Joined: Sep 2012
Posts: 5,462
DFW
DBMaster Offline
DBMaster  Offline
Joined: Sep 2012
Posts: 5,462
DFW
I don't know how accurate the electronic brake fluid moisture detectors are but I tested the fluid in a plastic bottle that had been opened and re-capped for over four years and it still tested as being fine. I've never even thought about it in the past (my pre-BITOG days) and haven't had issues yet.

Re: Open Brake Fluid [Re: coopns] #4634962
01/14/18 06:06 PM
01/14/18 06:06 PM
Joined: Mar 2008
Posts: 7,349
USA
slacktide_bitog Offline
slacktide_bitog  Offline
Joined: Mar 2008
Posts: 7,349
USA
chuck it, especially if it's a plastic bottle.

If it's a metal can, it will probably be OK.

If you're just using cheap DOT 3, you can get a new bottle of that anywhere. Now if iot was something more premium and expensive, then I could see the point of using the remainder.

Re: Open Brake Fluid [Re: coopns] #4634975
01/14/18 06:20 PM
01/14/18 06:20 PM
Joined: Jan 2017
Posts: 368
NJ
JLawrence08648 Offline
JLawrence08648  Offline
Joined: Jan 2017
Posts: 368
NJ
Once the cap is off, it pulls moisture from the open space in the bottle. I wouldn't worry about it, it's more important to change your fluid then worry about a little bit of moisture in the air in the bottle.

Re: Open Brake Fluid [Re: coopns] #4634977
01/14/18 06:22 PM
01/14/18 06:22 PM
Joined: Jun 2005
Posts: 11,623
Santa Barbara, CA
bdcardinal Offline
bdcardinal  Offline
Joined: Jun 2005
Posts: 11,623
Santa Barbara, CA
Even in a low humidity environment unless we are talking a bottle of Castrol SRF, brake fluid is so cheap it isn't worth saving opened bottles.


2014 Ford Mustang GT Track Pack
1995 Ford Mustang GT

Ford/Mazda Parts Counter
NRA Benefactor Member
Opinions expressed are my own.
Re: Open Brake Fluid [Re: coopns] #4635122
01/14/18 08:25 PM
01/14/18 08:25 PM
Joined: Jun 2003
Posts: 33,595
ME
eljefino Offline
eljefino  Offline
Joined: Jun 2003
Posts: 33,595
ME
A half full bottle in a garage is better than a vented master cylinder in a car driving in weather and seeing heat cycles.

If the fluid's still clear/ amber, run it. At worst use it as a pre-flush when bleeding then finish with something new.

Re: Open Brake Fluid [Re: coopns] #4635243
01/14/18 11:01 PM
01/14/18 11:01 PM
Joined: Sep 2004
Posts: 7,836
Marshfield , MA
andyd Online content
andyd  Online Content
Joined: Sep 2004
Posts: 7,836
Marshfield , MA
Wet brake fluid is better than no BF in a pinch, As long as it didn't freeze, it would be fine in a Hydraulic clutch. Also you could squish the bottle until the level was up even and put the top on. I use left over BF to set up airlocks when I bleed.


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: Open Brake Fluid [Re: coopns] #4635351
01/15/18 04:17 AM
01/15/18 04:17 AM
Joined: Jan 2011
Posts: 2,837
N.Ohio
Lubener Offline
Lubener  Offline
Joined: Jan 2011
Posts: 2,837
N.Ohio
I have used previously opened (2-3 years) bottles of brake fluid and never had a problem. As long as it is tightly sealed, I wouldn't worry.


The "thinking" man's friend.
Re: Open Brake Fluid [Re: coopns] #4635876
01/15/18 03:23 PM
01/15/18 03:23 PM
Joined: Jan 2016
Posts: 339
Cheshire, England
barryh Offline
barryh  Offline
Joined: Jan 2016
Posts: 339
Cheshire, England
The way I look at it is the fluid in your car is vented to atmosphere via the reservoir cap. The fluid in your bottle or tin is sealed. Which is going to deteriorate quicker ?

The whole thing about throwing unused brake fluid away once opened is ridiculous. If it lasts 2 years in a car that regularly sees 99% relative humidity it's going to last more than 2 years in the tin on the shelf in my dry garage. I would and did choose a tin container over a plastic bottle.


Barry

1979 BMW R45 (Triple QX 5W40)
2009 Mercedes C180K (Shell Helix Ultra 5W40)

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