Despite what may be claimed by silicone retailers the fluids may NOT be
compatible as the seals used first with DOT fluids will react by swelling if
used with silicone and should be replaced if you are going to change fluid
types. There is no reason to suspect the reverse will not apply. This is one
of the reasons why silicon has a bad name, especially amongst those who do not
read the words on the tin! It could also explain why there is a greater
resistance to the pistons returning to their correct locations and increasing
the residual line pressures until they start locking on.
First look for the reason why (or where) the existing fluid has gone before
going further with your system. It is pointless topping up just to see it
drain away again.
You may find information in:-
"Operating Performance of Motor Vehicle Braking Systems as Affected by Fluid
Water Content" Radlinski, Forthofer, Harvey, SAE 710253"
"Numerical Prediction of Brake Fluid Temperature Rise During Braking and Heat
Soaking" Lee, SAE 990483"
"Development of an Alarm for Moisture Content in Brake Fluid" Lee, Lin, Gau,
Lin, SAE 990475"
"Experimental Study of Auto Brake System Temperatures", Emery, Kumar, Firey,
Washington State DOT, Report WA-RD 434.1, July 97"
"A Study on the Service Interval Performance of Porated and Non-Borated Glycol
Ether Brake Fluids, Morsink, vn Grieken, deJong, SAE paper 2001-01-0947"
"Brake Fluid Vaporization as a contributing factor in Motor Vehicle
Collisions" Hunter, Cartier, Temple, Mason, SAE 980371"
There are many other papers with info on brake fluids if you search about.
The site at:
http://www.shotimes.com/SHO3brakefluid.html
is fairly helpful .
Guy R Day
A-H Sprite MkIV
----- Original Message -----
From: "Allen Hefner" <ajhsys@gmail.com>
To: <SDOliner@aol.com>
Cc: <spridgets@autox.team.net>
Sent: Monday, March 27, 2006 5:36 PM
Subject: Re: Brake fluid question
> Are you sure it is silicone? I don't know of any test, other than putting
> some on a painted surface and seeing if the paint goes away (not silicone).
>
> I do remember hearing that the seals could be a problem when changing
> fluids. That was basically going from DOT4 to silicone after not doing
> anything to an old system. It could be a problem going the other way as
> well.
>
> The fuids themselves are compatible. If this is a properly maintained
> racecar (spelled backwards that would be...er...racecar!) the seals and the
> brake system should be in top condition. If they aren't, they should
> probably be rebuilt to maintain safety in racing.
>
> Allen Hefner
> Norristown PA
>
>
> On 3/27/06, SDOliner@aol.com <SDOliner@aol.com> wrote:
>>
>> In a message dated 3/27/2006 10:37:10 AM Eastern Standard Time,
>> ajhsys@gmail.com writes:
>> DOT4 is compatible with the little bit of silicone that will be left.
>> I thought that if you switched, you had to change all the seals.
>>
>> I have silicone in TR and it is darn expensive every time I mess with the
>> brakes.
>>
>> David Oliner
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