why *must* brake fluid go bad?

jonko

jonko

Well-known member
Random question. We all know brake fluid is hydrophilic and will go bad if left in an opened container. My question is, why does this have to be the case? I have noticed that the brake fluid container is not airtight after opening. If I squeeze out all the air in the container, then close the lid tightly, the container reinflates after a day or two. Why doesn't the manufacturer make an airtight lid?
 
auntiebling

auntiebling

megalomaniacal troglodyte
Staff member
cost/benefit

the cost to make a container airtight enough to say it's good (and have the lawyers sign off on it) for a positive number of days is astronomical, especially when it means a net loss in sales.
 
ST Guy

ST Guy

Well-known member
auntiebling said:
cost/benefit

the cost to make a container airtight enough to say it's good (and have the lawyers sign off on it) for a positive number of days is astronomical, especially when it means a net loss in sales.
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This. Plus ya never know if some bozo won't put the lid back on properly and get all lawsuit happy when his "fresh" brake fluid fails him.

As for the fluid itself, it's just one of those things where modern science hasn't found a better brake fluid yet. Lots of things are that way. Progress in certain areas is sometimes slow.
 
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87cr250r

Well-known member
When they say don't use fluid from an open container they mean an open container, not an opened container. If you put the lid back on after you are done, the fluid does not go bad.
 
afm199

afm199

Well-known member
87cr250r said:
When they say don't use fluid from an open container they mean an open container, not an opened container. If you put the lid back on after you are done, the fluid does not go bad.
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no if you put the lid back on it lasts longer than a sealed container. It still goes bad
 
jonko

jonko

Well-known member
for what it's worth, i found that if I squeeze the air out, put some packing tape on top, then screw the top back on, the seal is airtight.

I'm going to assume it'll last until i need to use it.

Jon
 
afm199

afm199

Well-known member
Brake fluid is CHEAP. Your brakes are the most important safety mechanism on your bike. Why would ANYONE risk their life to save $5 or $10 once or twice a year? That totally befuddles me.
 
ST Guy

ST Guy

Well-known member
Stormdragon said:
Convert to DOT 5. (not 5.1) Problem solved! :laughing
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I wouldn't be recommending 5.0 here as someone may actually try it with disastrous results. Just straight forward advice. (Sorry, the "laughie" might not be enough to inform a reader you're just joking.)

:ride
 
Motech

Motech

_-_-_-_-_-_
ST Guy said:
I wouldn't be recommending 5.0 here as someone may actually try it with disastrous results. Just straight forward advice. (Sorry, the "laughie" might not be enough to inform a reader you're just joking.)

:ride
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True. I was tempted to correct him. Unless you're racing and changing it out a LOT, DOT 5 is a hazard.
 
Burning1

Burning1

I'm scareoused!
Motech said:
True. I was tempted to correct him. Unless you're racing and changing it out a LOT, DOT 5 is a hazard.
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:wtf

No racer in the world would even consider a DOT 5 fluid. And most racers will change their brake fluid on a regular basis, in order to deal with the breakdown of DOT 4 fluid.
 
ThumperX

ThumperX

Well-known member
Why not flush the system and use the entire bottle? The brake system will be happy (especially if it has ABS) you don't feel like you're wasting the fluid.
 
afm199

afm199

Well-known member
Dot 5 is great on military vehicles and taxis. It's no big deal to bleed brakes, and the fluid is cheap. Never understood the hullaballo.
 
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87cr250r

Well-known member
DOT 5 has a higher boiling point and it's not hydroscopic. But, the fact that it's not hydroscopic is why it shouldn't be used in our brake systems. Most brake systems have bleeders at the high points to let air out. Water is heavier than brake fluid. A non-hydroscopic fluid will precipitate water to the lowest points of the system where it cannot be removed through the bleeders. This water will eventually cause corrosion and stuck caliper pistons. This is why I will avoid DOT 5 brake fluid in all of my vehicles... though my latest truck purchase may use DOT 5 fluid (it's military). The brakes work well so I haven't exactly bothered to look at them yet.

The other more minor issue with DOT 5 is the sponginess. DOT 5 fluid traps air bubbles well. That just means you have to give the fluid a chance for the bubbles to coagulate before you bleed it after a fluid flush or system fill.
 
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ST Guy

ST Guy

Well-known member
afm199 said:
Dot 5 is great on military vehicles and taxis. It's no big deal to bleed brakes, and the fluid is cheap. Never understood the hullaballo.
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Don't quite understand the reason DOT 5 is used at all unless it's a vintage car and someone's concerned about the paint. While DOT 5 won't absorb moisture, moisture still gets in the system and goes to the lowest point, usually the calipers. So, regular changes are still required.
 
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