Subject: Re: [Healeys] Brake Fluid -- Silicone vs. glycol

From: Bob Spidell <[email-masked]>
Date: Sun, 25 Jul 2021 16:13:22 -0700

I'd add that DoT5/Silicone BF should be flushed occasionally (like, 
every 5-10 years). It doesn't absorb moisture, but supposedly water can 
pool in low spots (you'll get some condesation in the reservoir every 
time you check the level). I usually have to do something to my brake 
systems that often anyway. I've noticed that DoT5, which is purple 
coming out of the bottle, turns clear/amber near the wheels where, of 
course, heat is generated.

bs

ps. I've followed several threads where owners are reporting 
crystallization or gelling of Dot3/4, and no one has come up with a 
definitive cause.

On 7/25/2021 3:36 PM, Gary Anderson via Healeys wrote:
> Having co-authored the book on restoration of Austin-Healeys and been 
> involved in classic cars for over 30 years, I've confronted this 
> question in many forms and many times. I've talked to vintage racers 
> and great collections managers on whose decisions thousands of dollars 
> and human lives can depend.
> Out of all this, the simple neutral answer depends on how you will use 
> the car.
>
> Assuming you've replaced the complete brake system AND all seals and 
> gaskets, then:
>
> If you use your classic car regularly and maintain it carefully, then 
> by all means use glycol-based fluid and change it at least every two 
> years (more frequently if you're racing and/or doing long tours).
>
> If you don't use your classic car regularly -- it's parked for months 
> on end or used for display and show rather than regular driving and 
> touring -- then use silicone fluid.
>
> Regarding the proviso above, if you're not changing gaskets and seals, 
> then use whatever fluid was used before, but with glycol replace it 
> every two years at minimum and with silicone, check the level 
> frequently and top up as necessary.
>
> Let me know if you can find a classic collection manager or racing 
> driver who will disagree with that answer.
>
> Best
> Gary Anderson
>

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From: Tom Felts via Healeys <[email-masked]>
Date: Sun, 25 Jul 2021 20:14:00 -0400 (EDT)

I have used silicone in my Healey and E-Type for years and do lots of driving in them.  The only problem o had was not changing it when I should and the water pooled in the caliper pistons and they ultimately froze due to rust. 
----- Original Message -----
From: Gary Anderson via Healeys <[email-masked]>
To: [email-masked]
Sent: Sun, 25 Jul 2021 18:36:58 -0400 (EDT)
Subject: [Healeys] Brake Fluid -- Silicone vs. glycol

Having co-authored the book on restoration of Austin-Healeys and been
involved in classic cars for over 30 years, I've confronted this question
in many forms and many times. I've talked to vintage racers and great
collections managers on whose decisions thousands of dollars and human
lives can depend.
Out of all this, the simple neutral answer depends on how you will use the
car.

If you use your classic car regularly and maintain it carefully, then by
all means use glycol-based fluid and change it at least every two years
(more frequently if you're racing and/or doing long tours).

If you don't use your classic car regularly -- it's parked for months on
end or used for display and show rather than regular driving and touring --
then use silicone fluid.

Regarding the proviso above, if you're not changing gaskets and seals, then
use whatever fluid was used before, but with glycol replace it every two
years at minimum and with silicone, check the level frequently and top up
as necessary.

Let me know if you can find a classic collection manager or racing driver
who will disagree with that answer.

Best
Gary Anderson

[email-masked]

---

From: Simon Lachlan via Healeys <[email-masked]>
Date: Mon, 26 Jul 2021 09:49:11 +0100

I was getting myself in a muddle over brake fluid once so I made myself some
notes. Probably pinched from Google; I don't recall:-

1)	All brake fluid is "synthetic".it's not a "natural" product.
2)	Most synthetic fluids are NOT silicone. They are polyethylene glycol
ether based.
3)	DOT 3 & 4, which can be mixed, are not silicone. They are glycol.
4)	DOT 5, which cannot be mixed with 3 or 4, is silicone. Can't be
mixed with anything!
5)	DOT 5.1 is glycol based and cannot be mixed with DOT 5.
6)	DOT 5.1 can be mixed with DOT 3 or 4, as both are glycol based.

The word "synthetic" began to appear when manufacturers worked out that it
made regular brake fluid sound more special ie they could charge us more
money for the same old stuff.

DOT stands for Dept. Of Transport and relates to the fluids' boiling points.
If a car brakes at high speed, the brakes get hot. Some heat is carried away
from the brakes by the brake fluid. Bad news if the fluid boils! The faster
you're going, the higher DOT you need. Higher DOT numbers indicate higher
boiling points for "Dry" fluid (has not absorbed any water) and "Wet" fluids
(has absorbed water). ie, the wetter it is, the more problematic it becomes.
Mixing 3 with 4 lowers the boiling points and vice verca.

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