<VV> brake help

Hugo Miller hugo at aruncoaches.co.uk
Wed Jan 23 22:22:01 EST 2019

Interesting to note that most modern cars have rubber diaphragms on top 
of the reservoir to prevent moisture absorption. I don't know where I 
read that story about moisture separating out from silicone fluid and 
pooling. I am sure it was from a reputable source. Maybe the same source 
that stated that you would get a less firm pedal with silicone fluid, 
although again I can't remember why that should be so.
Of course a lot of these things are theoretical and have no discernable 
effect in the real world.

On 2019-01-23 21:25, Frank DuVal via VirtualVairs wrote:
> I can tell you from almost 40 years of DOT 5 use that this internet
> warning is a bunch of hokum, like most unsubstantiated things one
> reads on the Internet, HA!
> I give real world experience I have with the product.
> Not being hygroscopic is the benefit of DOT 5, not a problem to be
> reckoned with. If it was, I would have line failure from the inside 
> on
> my cars sometime during the last almost 40 years. Always rust from 
> the
> outside in is the cause.
> I will say I never used DOT 5 in a system using DOT 3 without
> rebuilding the system. Why would I? I’m trying to make a brake system
> that lasts for years, not pour expensive fluid in with who knows 
> what,
> including all that d#$& white corrosion that DOT 3 brake systems have
> after a few years.
> Frank DuVal
>> On Jan 23, 2019, at 7:15 PM, Hugo Miller via VirtualVairs 
>> <virtualvairs at corvair.org> wrote:
>> I presume the significance of your living near the ocean is that 
>> there is more moisture in the air? I have heard that since silicone 
>> fluid isn't hygroscopic, any moisture in the system will 'pool' at the 
>> lowest points & just sit there causing corrosion, rather than mixing 
>> with the fluid (where it can be flushed out every time you change 
>> brake fluid).
>> I have no idea whether that is correct, but to me it is just another 
>> reason to be wary of silicone fluid, since its major advantage might 
>> in fact be a disadvantage.
>>> On 2019-01-23 16:10, Steve Gangi via VirtualVairs wrote:
>>> I'd like to add my two cents as a rubber chemist.  1. When a new
>>> rubber seal is exposed to a fluid for the first time it becomes
>>> conditioned to that fluid (swells) and takes a set. When that fluid 
>>> is
>>> removed, the rubber slowly recovers (shrinks). DOT 3 brake fluid 
>>> and
>>> Silicone are very different. They do not mix and cause different
>>> swelling. Once a brake part has been swelled once in DOT 3 it will 
>>> not
>>> re-swell to the same dimensions in silicone and probably leak. 2. 
>>> If
>>> you are putting silicone into a system previously containing DOT 3 
>>> you
>>> should at least clean the system with alcohol and dry out 
>>> completely
>>> by blowing compressed air through the lines. Then take apart the
>>> cylinders and wipe all the rubber cups off with alcohol. If you are
>>> going to go through all that, you might as well put in new rubber 
>>> cups
>>> or new wheel cylinders. I have had similar experiences as many of 
>>> you;
>>> great results with new parts and mixed results taking short cuts. I
>>> live near the ocean and silicone is a necessity for old cars. Steve
>>> GangiBranford, CT6 Corvairs
>>> ___
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