Two years ago, I rebuilt the brake MC on Miss Molly the '79 Midget,
because, among other things, she had the muck described in the MC
reservoir. After rebuilding, I flushed the system and replaced the fluid
with DOT 5 silicone (under the FWIW department, before rebuilt it, I did
let the seals, etc, soak a day or two in the fluid to check for adverse
effects).
The muck came back pretty quickly and I flushed the system again. It
came back again, in a lesser quantity. Because I had suffered no loss of
braking, nor did the MC, calipers or wheel cylinders lose/leak fluid, I
determined that the flexible lines were deteriorating from the inside.
This year, I replaced the brake MC (the bore on the old one was on the
thin line of acceptability), and all the flex lines. I also did a more
complete job of flushing the system by removing the calipers and wheel
cylinders and flushing them separately (the stuff that came out of them
was scary), as well as forcing brake cleaner through the hard lines.
All of the components and seals in the system are now new/replaced within
the last two years. I have not had a piece fail because of the silicone
fluid. I have had pieces fail because of wear and age.
Conclusions:
* Black muck is probably the flex lines deteriorating from the inside,
and being sucked back up into the MC.
* Silicone fluid will not harm your system *if* you start out with
new/rebuilt components, and a completely clean and dry system, then
regularly flush/replace the fluid (I'm on a two year schedule for that) .
Your Mileage May Vary.
Rich
Council Bluffs, Iowa
'74.5 RB MGB "Miss Maggie"
'78 Chevy Half-Ton "Waltzin' Matilda" (LBC Support Vehicle)
'79 Midget "Miss Molly"
richard.arnold@juno.com or rdarnold@neonramp.com
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