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Brake Fluid Shelf Life


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Hey guys,

I have a bottle of Honda brake fluid on my shelf that has been sitting for probably 2 years with the cap on. I know it says to always use brake fluid from a sealed container so I'm wondering if this stuff is still okay to use or do I need to use new fluid from a container with the foil seal on top? It's no big deal if it's no good anymore I just figured I would check. Thanks in advance!

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Hey guys,

I have a bottle of Honda brake fluid on my shelf that has been sitting for probably 2 years with the cap on. I know it says to always use brake fluid from a sealed container so I'm wondering if this stuff is still okay to use or do I need to use new fluid from a container with the foil seal on top? It's no big deal if it's no good anymore I just figured I would check. Thanks in advance!

 

I think they recommend 1 year with a tight cap. I've gone over 2, but not 3 with no issues. I always write the open date on all fluids with a open shelf life.

 

Mike

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Okay it has gone through several lovely Pennsylvania season changes in our un-heated garage so it'll be interesting to see what it looks like. Thanks for the tip on color!

 

there are also test strips you can buy that will tell you the moisture content of your fluid if you want to get real technical.

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This is kind of a side discussion but I found it interesting at the time-

Back in auto shop class our professor gave us a cool demonstration of the hygroscopic properties of brake fluid. He filled a shot glass to the very brim with DOT 3. Then proceeded to add almost another full shot glass of water to the already full shot glass of brake fluid. It took almost the whole glass of water before overflowing. It was really kind of mind blowing. His point was that there are enough free spaces in the brake fluid molecule to accept one hell of a lot of water. And the brake fluid sucks it down like a magnet.

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This is kind of a side discussion but I found it interesting at the time-

Back in auto shop class our professor gave us a cool demonstration of the hygroscopic properties of brake fluid. He filled a shot glass to the very brim with DOT 3. Then proceeded to add almost another full shot glass of water to the already full shot glass of brake fluid. It took almost the whole glass of water before overflowing. It was really kind of mind blowing. His point was that there are enough free spaces in the brake fluid molecule to accept one hell of a lot of water. And the brake fluid sucks it down like a magnet.

Damn, I had no idea. I just slam dunked a dusty bottle of God knows how old brake fluid directly into the ol garbage can!! GREAT INFO. Edited by Rooster72
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Hey guys,

I have a bottle of Honda brake fluid on my shelf that has been sitting for probably 2 years with the cap on. I know it says to always use brake fluid from a sealed container so I'm wondering if this stuff is still okay to use or do I need to use new fluid from a container with the foil seal on top? It's no big deal if it's no good anymore I just figured I would check. Thanks in advance!

 

DOT 4 brake fluid is glycol based, meaning it absorbs water and condensation making it part of the fluid.  Silicone brake fluid (DOT 5) is highly effective but does not absorb water, so brakes perform horribly when the slightest bit of condensation builds on the inside of the brake lines.

 

All this to say, your glycol based fluid should be ok if it's been in a consistent cool place, without a lot of humidity fluctuations.  Otherwise, it could have developed too much condensation and thus deteriorated the fluid's effectivenes.

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This is kind of a side discussion but I found it interesting at the time-

Back in auto shop class our professor gave us a cool demonstration of the hygroscopic properties of brake fluid. He filled a shot glass to the very brim with DOT 3. Then proceeded to add almost another full shot glass of water to the already full shot glass of brake fluid. It took almost the whole glass of water before overflowing. It was really kind of mind blowing. His point was that there are enough free spaces in the brake fluid molecule to accept one hell of a lot of water. And the brake fluid sucks it down like a magnet.

I'm all about peace of mind with my bike and this is just enough info to freak me out haha. I had no idea brake fluid could absorb that much water. I think I'm just gonna start with a brand new bottle when I bleed my brakes, it's cheap insurance.
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