[Healeys] Brake Fluid -- Silicone vs. glycol

[s.hutchings at rogers.com]

I’ve used DOT 5 silicone fluid for many years, and no problems.
My only reservation with it is - if something goes wrong with your servo, the fluid will be sucked through the manifold into the engine, and you don’t want that!
I’ve changed the size of my master cylinder and bypassed the servo so that I can continue to use DOT 5. Again, no problems, but I do tend to do some work on the brakes often enough to change the fluid within the required period.

Stephen, BJ8

Sent from my iPad

> On Jul 26, 2021, at 5:16 PM, Richard Collins via Healeys <healeys at autox.team.net> wrote:
> 
> I had one and it worked well. Lasted about 2 years.
> My wrench has one and swears by it. But other than the Healey, I track my cars so change fluid frequently. DOT4 HiTemp for them, DOT4 regular for the Healey. No problems.  Never used silicone even though I completely rebuilt and or replaced the Healey system last year (calipers, drums, and lines)
> 
> Regards,
> Richard C
> BN7 440
> 
>> On Jul 26, 2021, at 15:26, Roger Grace via Healeys <healeys at autox.team.net> wrote:
>> 
>> 
>> Does anyone have an opinion as to the accuracy of those cheepo pen style brake fluid moisture detectors ?
>> You dip the probes into the reservoir and they give led indication for range % moisture present.
>> Just wondering ... ??
>> rg
>> 
>>> On Mon, Jul 26, 2021 at 4:55 AM bluehealey <bluehealey at gmail.com> wrote:
>>> Now that is a perfect checklist Simon. Captures everything you need to know. 
>>> In addition I work on the basis that glycol mixtures, if neglected (not flushed) for more than 3-4 years, can cause minor problems with the hardware. 
>>> Silicone, if neglected for a similar period, can cause major problems with the hardware. 
>>> Guess which I choose to use. 
>>> 
>>> AlanB - iPhone message.
>>> 
>>> > On 26 Jul 2021, at 09:57, Simon Lachlan via Healeys <healeys at autox.team.net> wrote:
>>> > 
>>> > 
>>> > 
>>> > 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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