Be aware that all brake fluids are
Hygroscopic, which is that is that they absorb moisture.
You can't stop it; your brake fluid is taking water
from the air right now ! That's why we always keep our
DOT3/4 whatever, in a sealed container.
So what happens when the water content
of your brake fluid gets too high ? Well, the disc gets
flippin' hot, the calliper gets flippin' hot, the fluid
in it gets flippin' hot, that's what. What happens to
water when it boils ? It turns into steam darn quick
is what. They used to run trains on the stuff. Steam
expands quickly and under enormous pressure, so where
can it go ?
The answer is it expands fast and
slams your brakes full on, Wham !
Not a nice scenario, so the rule is,
change the fluid completely, every two years (three
at the most). Check the colour, it's clear when you
pour it from a sealed container. Pale yellow is 1to
2 years old.
Yours is heading toward brown ?, then
it should have been changed at least a year ago, probably
Dot 3 and Dot 4 hydraulic fluids are
both Glycol based and can be mixed.
So you can top up or replace your Dot 3 with Dot 4 fluid
if that's what you've got (Dot 4 is better).
You can't do this the other way around though; if your
system says to use Dot 4 then you can't go backwards
to Dot 3, you must use Dot 4 only
There is now a Dot
5 fluid (for extreme conditions, we don't go there)
Dot 5 is not compatible with Dot 3 / 4 under any circumstances,
don't use Dot 5 unless your system is designed for it..
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