Re: Master cylinder

[jlandry@domain.elided (John A. Landry)]

In a brilliant stroke of genius, cookiedan@domain.elided (Daniel Nees) blurted
out:

>I was just Manderisming while getting washed a few minutes ago. Since
>I'm going to be replacing my master cylinder this weekend, should I
>flush my entire system out and add silicon fluid instead of Dot 3 stuff?
>If I go silicon do I have to change calipers and wheel cylinders, or is
>just a good flushing enough? Or should I just forget the idea and put a
>good master cylinder on?

I remember from past reading that in order to convert to silicone brake
fluid, you need to *completely* flush the brake system with *alcohol* to
remove every trace of the old non-silicone brake fluid.  DOT 3/4 and DOT 5
(silicone) fluid are not compatible and won't blend.  I seem to recall the
preferred procedure was to go ahead and completely disassemble the calipers
and cylinders in order to get all the old brake fluid out, which is not
always possible when you don't disassemble.

Another thing to consider... while it's true that one of the benefits of
silicone fluid is that it doesn't absorb moisture, because of the very fact
it doesn't absorb moisture, any water that finds it's way into the system
(or old fluid that remains) will pool in low places and cause internal
rust.  With normal DOT 4 fluid (like that made by Castrol), some moisture
will be absorbed over time and assimilated into the fluid and held there by
the brake fluid.  It will then be flushed out during regular brake systems
flushes (which everyone does... right?).

I *think* DOT 4 fluid has a higher resistance to moisture absorption and
boiling than DOT 3 does, so even though it may absorb some moisture, it's
still very safe for our type of vehicles.

I'd consider sticking with DOT 4 fluid and not messing with the potential
hassles of trying to convert to silicone fluid.  Silicone fluid has it's
place, but I'm not so sure any benefits in your rig will outweigh potential
hassles.  I mean, after all, you're not trying to stop a high speed race
car!

Just a thought.

John L.
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