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Re: How to? DOT 4/5 to silicone?

To: Triumphs@autox.team.net, Bitparts@aol.com
Subject: Re: How to? DOT 4/5 to silicone?
From: "Kurt Oblinger" <Kurt_Oblinger_at_AWP450@mail.hq.faa.gov>
Date: Wed, 13 Mar 96 15:23:42 EST
>Just rebuilt the driver's side rear cylinder. Have the car up on blocks and
>thought it would be a good idea to change out the brake fluid.  Have no idea
>what the best way to change out the old DOT to silicone would be. Help!!!


I've done some extensive reading on the use of DOT5 (silicone) brake fluid as
I plan to use it in my Vitesse I'm doing a ground up on. If you ask 10 different
people you'll get 10 different answers. Afetr sifting through all the 
information and soliciting opinions here are my conclusions.

If you try and install DOT5 in an existing system that had DOT3/4, no matter
how thoroughly you flush the system, you will have problems. The two fluids are 
fully miscible and will not react with each other. However, how the DOT5 reacts
with the seals in the braking system is in question. The result will probably 
leaks. I don't have all my research in front of me and I don't want to try and 
quote technical information from memory. However, what I concluded is that the 
only reliable way to transition from DOT3/4 to DOT5 is to completely rebuild the
braking system, replacing all seals in each component, and flushing the lines 
thoroughly with denatured alcohol and the blowing them out with air. Flexible 
hoses should be replaced as well. In all cases that this process has been 
followed that I am aware of, for a DOT5 installation, there have been no leakage
problems.

Your best bet would be to flush thoroughly with DOT4 LMA fluid and then reflush 
the system yearly as part of normal maintenance.

Hope this helps.
Kurt Oblinger
Redondo Beach, Ca.


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