Classic Mustangs List Archive

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Mail From: Paul Prince (email redacted)

Mustang Monthly stated that we should never use Silicone Brake Fluid but
never explained why.

I have been using it in my '65 for 8 years and never had a problem. What is
the consensus out there? Has new evidenced surfaced that says silicone is
bad?

Thanks...

Paul Prince
1965 Mustang 2+2
1989 Mustang GT Convertible


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Mail From: David McCracken (email redacted)

> I have been using it in my '65 for 8 years and never had a problem. What
is
> the consensus out there? Has new evidenced surfaced that says silicone is
> bad?
>
> Thanks...
>
> Paul Prince


I use it exclusively in my restorations because it will not absorb water,
damaging the internals of the brake system, and also because it will not
harm paint. The only problem which I have experienced is that once in a
while an item such as a wheel cylinder or brake proportioning valve will
leak, causing the part to have to be rebuilt. These types of leaks always
occur while the vehicle is setting in storage so it is not really a safety
issue. The rubber parts are designed so that when regular brake fluid is
used with them, they swell slightly, creating a tight seal. Silicone fluid
will not swell the rubber. This small inconvenience is far outweighed by
the advantages, especially in a collector car which is not driven daily. I
highly recommend using silicone brake fluid in collector cars.

David


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Mail From: Stephen Mirsky (email redacted)

I've done alot of reading on this. Silicon brake fluid has a softer pedal
feel (supposedly) than regular brake fluid. The main problem with it is
that it doesn't take high temperatures well. So it's great in cars that sit
for long periods of time, because it doesn't mix with water, which is great
for your classic that sits in your garage and is drivin only on the 4th of
July parade or whatever. As far as daily drivers, it's not really
recommended for that. It also doesn't work at all with ABS systems (we
don't have to worry about that unless you have some insane restomod...)

Also, I've read that to change over, you have to replace all the brake
parts, but that flushing the system with alcohol works the same.

You won't find silicon fluid in any sort of race car whatsoever... so think
of it that way

-steve in nj-
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This read-only message was archived from a public mail list.
Mail From: Scott Hall (email redacted)

On Tue, 1 Feb 2000, Paul Prince wrote:

> Mustang Monthly stated that we should never use Silicone Brake Fluid but
> never explained why.

in my experience, mustang monthly is worthless for almost everything.
you'd think that people that write an enthuiast car magazine should know
about the cars and how they work.

> I have been using it in my '65 for 8 years and never had a problem. What is
> the consensus out there? Has new evidenced surfaced that says silicone is
> bad?

silicone fluid, when mixed with glycol fluid, can (to oversimplify) clump.
this doesn't happen with all glycol fluids, so it depends on what you have
in it before you switch. I've heard it recommended that you flush the
system with alcohol first, but I've seen people just flush with silicone
without problems. the other problem is that glycol fliuds cause rubber
parts to swell. silicone won't. so, when you switch, you can get leaks,
and if the fluids aren't compatable, some of the glycol fluid in the seal
will react with the silicone, which is bad. then there's the issure of
the silicone itself. the silicone will not absorb water. this is good
and also bad. good, for all the reasons you might think, but bad because
what you can end up with instead is 'pools' of water in the fluid, which
is worse. as well, the silicone doesn't perform as well as the glycol
fluid will when actually subjected to more severe braking situations.

in my car I use glycol fluid. if I drove it once a year, I might switch.
otherwise, I think glycol is the better choice.

scott


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Mail From: Gordon Couch (email redacted)

I have to disagree here. Silicone fluid has a much higher temperature rating
than standard brake fluid and can take the heat better. Plus it will help the
brake disipate the heat generated as it has a better thermal coefficient. Also,
it does not absorb water and does not have to be replaced as does the glycol
based DOT3.

As for the "softer" pedal feel - there should be no difference between silicone
and glycol based fluid. Hydraulic systems work because the fluid does not
compress. Water could be used in the system for that matter. Of course if you
use water, you'll oxidize the system, so I don't recommend it.

Silicone is largely non-aggressive to most pliable members of the brake system,
the exception is natural rubber. Silicone will be absorbed by natural rubber and
causes early failure. However, if you have replaced the flex lines you probably
have a synthetic material replacing the rubber and should not have a problem
with the silicone fluid.

Stephen Mirsky wrote:

> I've done alot of reading on this. Silicon brake fluid has a softer pedal
> feel (supposedly) than regular brake fluid. The main problem with it is
> that it doesn't take high temperatures well.


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