Re: Silicone Brake Fluid

[Glenn Merrell <gmerrel@domain.elided>]

Hello Mike and ALL,

    I love it when the experts in the field can not come up with
agreement on some basic engineering principals and applications, and yet
from two well known names, Locheed and Girling!  Ha!

So let's add up the score...Girling 2, Locheed 0, and a push on the
lubrication issue...maybe.  From my own Chemical Engineering Reference,
1.  Glycol/ester combinations will attract water, being listed as
hydrotropic;
2.  from every can of silicone DOT 5 I have read, the boiling temp
listed on the label is at least 150 degrees F higher than Glycol/Ester
based Dot 3;
3.  Again from my Chemical Engineers reference, silicone in liquid form
is listed as a lubricant;
4.  Silicone does not attack rubber seals, as esters will eat rubber and
glycol expands rubber...maybe not a problem now as most of the seals
made today are synthetic, but how much NOS is still out there in the
form of rubber seals replacement kits?

I would think that in application, a Stag in normal road conditions
would still benefit from a higher temp based fluid, and, if a fluiod
does not attract fluid readily, possibly would help maintain the system
if the cap is left in place.

When I am at the Vintage Races in Steamboat this weekend, I will query
the mechanics in the pit area and take special note of the concours cars
little tags on the brake fluid reserviour that says "silicone only"

Next step is to have these companies produce test results proving or
disproving their claims.  So, it an e-mail or two off to some of the US
manufacturers, but my calls to date simply respond with "use what the
auto manufacturer recommends" so they do not get into the liability
game.  Produce spec data sheets can be had for the asking.

The VTR research on the subject is at
http://www.vtr.org/maintain/brake-fluids.html   and one point well made
is since Silicone brake fluid does not miw with water that water may
actually pond in low spots and cause corrosion, exactly the symptom I
have found from systems using DOT3 and DOT4 fluids!

The wild debate continues....

Regards,
Glenn  Merrell

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