Re: Discussion, Please

[Steve Manning <stephenm@ix.netcom.com>]

At 09:57 AM 6/1/98 CDT, you wrote:
>This will probably start a new "thread from hell"....
>
>In response to a revent inquiry about silicone brake fluid, Brett D. 
>ocmmented that it is "imncompatible" with even small amounts of 
>standard brake fluid.
>
>This concerns me, as I have just finished draining the brake 
>system and honing the brake cylinders on my long-dormant 1958 Fiat 
>1200 Roadster.  I planned to use silicone brake fluid on re-assembly 
>just to avoid condensation and oxidation during subsequent short 
>storage periods.
>
>However, I had not heard this comment before.  I am certain there are 
>traces of brake fluid in the system.  I'm not sure how I would 
>eliminate them, unless I did something creative like pouring a quart 
>of denatured alcohol thru the system - which I am perfectly willing 
>to do.
>
>I welcome thoughts and (anatomically and logistically feasible) 
>suggestions....

It is not a good idea to mix silicone (DOT 5) brake fluid with any other
(DOT 4 or lower).  The best way to flush is just to flush with the new
silocone fluid (pressure bleeding is best).  Run a whole bunch through,
drive for a little bit, then flush again.  You'll never get every trace of
it out of the rubber hoses; they absorb some of it.  It's best to replace
them at the same time.  The hard lines will flush easy, and you've already
cleaned out the brake cylinders, so the master is the only major thing
left.  If you're really scrupulous you should replace that now also;
otherwise just flush it good (I'd take it out and do it manually).

I'd question using the silicone altogether, however.....it still has some
incompatibilities with older rubber, and it compresses more under pressure.
 What is always mentioned as its big benefit, not absorbing water, can also
be a problem.  Since water is going to get in anyway, and the silicone
fluid doesn't absorb it, it puddles in different places.  This can cause
rust in those places where that happens.

My practice is to use a good DOT 4 fluid (Castrol LMA, for example), and
bleed the system once/twice a year (usually right before winter storage,
and again in the springtime).  It's very quick once you get a system going,
and you flush out the water and any crud with the fluid.  I've successfully
done this for years on cars from the '50s, '60s, and '70s; foreign &
American, and haven't had any problems yet!

Yes, I realize some people swear by using the silicone stuff....this is
just my .02 from my experience and others.  Your brakes, your choice...no
flames, please!..............SLM

Steve Manning:  stephenm@ix.netcom.com
...Physical home: Metro D.C. area, USA
.....Virtual home:  http://www.stationwagon.com