Jerry:
I cannot categorically say that *all* DOT 5 is purple. What I
can say is that all DOT I have *personally* seen is purple.
No, they cannot be mixed. As I understand it that is why DOT 5
is purple, to prevent people from being confused and accidentally mixing
them. I am sure nothing dangerous would happen (explosions, noxious
fumes, liberal politics, etc) but it is certain that braking
effectiveness would diminish, and that in and of itself would be 'bad'.
You should be able to drain your existing fluid, purge the lines
with DOT 5, and then replenish and bleed using DOT 5 with no issues.
Your seals should be fine. Some will claim you are better off doing a
total rebuild using all new seals before converting, but I personally am
skeptical. DOT 5 is fully compatible with existing brake seal materials,
and previous exposure to DOT 4 should make no difference. DOT 5 WILL
attack silicone rubber, but that is a very unusual material to use in
braking systems.
DOT 4 and DOT 5 are not miscible (they will not mix) and DOT 5
will float on top of DOT 4. So I suppose you could remove a teaspoon of
your existing fluid, mix a teaspoon of the purple stuff, and see if the
blend together. If they don't then your existing fluid is not DOT 5.
The presence of trace amounts of DOT 4 will not degrade your
braking, since the two fluids will happily coexist, even if they won't
mingle. What will degrade your braking is water. DOT 5 will not absorb
water, but DOT 4 will up to a reasonable limit. If there is water in a
caliper, for example, DOT 4 will disperse it, and will function normally
although with a lower boiling point - perhaps 400F. DOT 5 will *not*
disperse it, so if the DOT 5 fluid reaches 212F, the wafer will boil and
you will experience the joys of brake fade.
DOT 5 will not attack paint, DOT 4 will. That alone is
sufficient reason for me to use DOT 5.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Jerry Guyot
Sent: June 07, 2005 12:11 PM
To: 6pack@autox.team.net
Subject: DOT 5 Silicone Brake fluid
I have a quick question regarding DOT5 Brake fluid. I bought a TR6 that
the
previous owner said that they had rebuilt all the master cylinders and
had
used "Silicone Brake Fluid" after the rebuilds. The brake master cyl
needs
fluid. I went out & purchased some DOT 5 (Gunk). That fluid is "purple"
so I
went out and bought another brand (NAPA) and that is also purple!!......
The
fluid in the master cyl is "Clear".
My question is, are all "Silicone" fluids purple? Can I mix the "purple"
& the
"clear" ?
Thanks for your help.
Jerry
71 TR6
CC58003L
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