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  #1  
Old 05-29-2008, 05:18 AM
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Question Brake Fluid Shelf life

Here's a question for you. How long can brake fluid sit in an unsealed bottle before it becomes unusable?

The reason I ask this is because I replaced the brake fluid on one car last weekend and I want to do another car this weekend. I have about half of one of those 1 quart bottles of fluid left over from the last job that I'd like to re-use. It's been sitting in the bottle with the cap on all week and I'd hate to waste it.

I'm already familiar with the hygroscopic properties of glycol-based fluids and the warnings about always using fluid from a sealed container, so you don't have to explain that part to me again, thank you.

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Old 05-29-2008, 05:20 AM
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I'm pretty sure it doesn't go bad...
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Old 05-29-2008, 07:59 AM
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Once the inner seal on the can is broken, about 2 years.
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Old 05-29-2008, 08:35 AM
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Kind of what I thought. Thanks, MB Doc.
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  #5  
Old 05-29-2008, 08:58 PM
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Well, I am new to this forum and my goal is not to challenge, but...
brake fluid sucks up moisture like there is no tomorrow, right? If this is true, I don't believe it could be kept for two years with a broken seal. Air and moisture can seep through the threads and feed the fluid with moisture. I don't think a couple of weeks would do harm but I think it is worth the purchase of new fluid if it has been sitting for some time.
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Old 05-29-2008, 09:21 PM
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Two years sounds about right to me (chemist) with some variation allowed for storage conditions. Two years in my MB is about the maximum I allow also. Must work, my calipers have only had pads replaced for the last 25 years.
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Old 05-29-2008, 09:29 PM
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Benz recommends changing due to hygro absorbtion every two years b/c the fluid in the reservoirs is open to ambient air humidity conditions thru the cap venting system.
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Old 05-29-2008, 09:31 PM
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Quote:
Originally Posted by Arthur Dalton View Post
Benz recommends changing due to hygro absorbtion every two years b/c the fluid in the reservoirs is open to ambient air humidity conditions thru the cap venting system.
That's my point too. Surly the can with the broken seal but a tight lid can be no worse than the reservoir.
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Old 05-29-2008, 10:05 PM
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Getting more involved and interesting, if...

1. MB suggests fluid replacement every two years because of ambient air humidity conditions thru the cap venting system, and
2. a tight lid can be no worse than the previous

then the fluid put in the car is already two years old and would need to be replaced by MB standards, if put into the car it would come out four years old, right?
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Old 05-29-2008, 11:05 PM
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When in doubt, throw it out.

When it comes to a life safety feature like brakes, or critical operational pieces like transmissions and cooling system, why not always use new and fresh?
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Old 05-29-2008, 11:34 PM
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<>


Who said it should be put in the car??

What was said is it could have a 2 year shelf life..just like the reservoir has.
One would not add a 2 year shelf life fluid to the res. b/c it has already expired it's 2 year shelf life.

The main point is the question was asked about a can that had been opened and recapped a week ago...that fluid would not have hygroscopic contamination to the point of non/use.
I think we are all in agreement , one way or another.
I purposely buy brake fluid in the plastic 1 quart containers so that after I use some , I squezze the bottle until the fluid rises and then recap it.

This gets most of the air out of the container and as the container attemps to reform to it's original shape [plastic memory], it creates a partial vacuum inside that helps the cap reseal well and limits the amount of air contained..........

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Last edited by Arthur Dalton; 05-29-2008 at 11:54 PM.
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