PS Magazine - TB 43-PS-586
PS, The Preventative Maintenance Monthly
ISSUE 586
SEPTEMBER 2001
PS 586
SEP 01
Here are two
other
ways to
tell what kind
of brake fluid
you have:…
Old fluids
should be
flushed!
See your
TMs for
details.
2.
Put some of the unknown fluid in
a jar with a little water and shake it.
BFS does
not
mix with water, and
you'll see distinct layers. DOT 3
and 4 fluids, on the other hand, do
mix with water and remain mixed.
You won't see separate layers.
1.
Try mixing a few tablespoons of
the unknown fluid with a little BFS.
If the two mix, the unknown fluid is
BFS, too. But if the two fluids sep-
arate into layers, the unknown stuff
is DOT 3 or 4. Your vehicle needs
to have the brake fluid changed.
PS 586
SEP 01
2
Brakes.
..
Use Only Silicone Brake Fluid
BFS, provided under MIL-B-46176 and also known as DOT 5 brake fluid,
replaced the old brake fluid, VV-B-680, also known as DOT 3 or DOT 4. BFS is
more stable at high temperatures and won't absorb water.
So, when it's time to add brake
fluid to a master cylinder contain-
ing BFS, make sure that what you
add is also BFS. A combination of
BFS with old fluids will still
absorb water, creating corrosion
and deposits which can cause
stopping problems.
Mixing old brake fluid with
BFS can also lead to seal leakage,
as the seal protective properties of
BFS are diluted by the old stuff.
So how do you tell which fluid is which? Go by the color, if you can. BFS is pur-
ple or blue in color, though the dye that gives it the color can break down. Then the
fluid in the master cylinder becomes brown or amber.
There's no cause for alarm if the color varies—the BFS is still good. But if the
color is not purple or blue, you can't tell what kind of fluid is in your brake system.
Mechanics,
there's only
one
type of brake
fluid for use in
military vehicles-
silicone brake
fluid
(BFS).
that’s
me!
BFS is
purple
or blue
Check
brake
fluid for
color
BFS + unknown fluid
Mix?
BFS, too
No mix?
DOT 3 or 4
Mix?
DOT 3 or 4
No mix?
BFS
Unknown fluid + water
586. 02-03 (C)
8/2/01
6:03 PM
Page 1
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