> Re/type of brake fluid to use and why. First, DOT3 fluid is not
>hydroscopic, it is hygroscopic,i.e. it will readily take up
moisture and
>retain it.
==========
Right, Dot 3 and 4 is hydroscopic. I was talking about Dot 5 which
isn't.
==========
Have you ever seen what happens to a steel can that has brake
fluid in it? Where the metal is bare it will rust in no time. Think
of what
is going on inside of your brake system! Moisture will enter even
through
the rubber components. The silicone fluid is a definite advantage
for two
>reasons 1) It"s boiling point is much higher.
==========
A moot point for street use.
==========
Why? Because it does not
>attract and retain moisture. When moisture is introduced into a
system, the
>fluids' boiling point goes down considerably. 2) By eliminating
moisture in
>the system, you eliminate the components corroding and sludge
forming also.
==========
Periodic bleeding negates this.
==========
>The belief that silicone is a cure all is also a falacy. People
think you
>can put it in and forget it. NOT TRUE. Though silicone fliud does
not
>attrach moisture, there is still moisture in your system.The system
is not
>air and water tight. What happens after awhile is the moisture that
entered
>the system will accumulate in the low spots of the system. No,it
will not
>mix with the fluid,but it is still sitting there and will lead to
rust and
>corrosion.
========
Yep, and according to my brake tech buddy, cars using Dot 5 have a
much higher percentage failure rate for this very reason. Cars using
Dot 3, 4 keep the moisture in suspension whereas Dot 5 allows
moisture to collect around caliper pucks. Another issue he pointed
out is that Dot 5 is thick enough to cause metering problems with
some late model ABS.
========
That is why it is recommended that even with silicone you bleed
>the system once a year, to rid the system of ANY moisture.
Whenever I
>restore a car ,I will replace all rubber components, flush the
steel parts
>w/ denatured alcohol or replace them,then add silicone fluid. I
have done
>this for the past 12 years and never have had a problem.
=========
FWIW, I have a '69 El Camino that hasn't had it's Dot 3 changed
since '71 when I converted it to disc brakes. My '75 Bricklin has
been bled once when I replaced the master cylinder last year. Like I
said; IMHO Dot 5 is overkill for the street and potentially is worse
for us lazy types.
GM
Hope this helps
>George.
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