Last week I asked for information from those who had converted from
mineral-based (DOT3/DOT 4) to silicon hydraulic fluid in brakes and did they
have any problems. The following is a summary of the responses and the
results of a simple experiment.
There were about 10 responses from folks who had drained their systems as
much as possible at the wheels and then put the new fluid in the MC and
continued to bleed till the new fluid flowed cleanly out of the wheel
cylinders. Some had done it recently and others had done it more than ten
years ago. All reported no problems.
There were several responses that said you must replace all seals and hoses
and flush the system with alcohol. They didn't indicate what would happen
if you didn't do this.
One person said to not worry, the two fluids don't mix, the silicon floats
on top the mineral based fluid. As a result, any remaining DOT 4 would end
up in the low spot --- the bottom of the wheel cylinders. He also said to be
sure not to shake the silicon fluid because air bubbles would become
suspended in the fluid and take a while to reach the surface.
I decided to run an experiment (engineering background) by pouring a small
amount of DOT 4 (nearly clear with a slight yellow color) into a small jar
and then adding an equal amount of the purple silicon fluid. Sure enough,
the purple stuff stayed on top. The mixture was then shaken vigorously and
let it set. A bunch of bubbles appeared in the upper part of the fluid and
the whole thing turned purple. So far, exactly as I was told . A half hour
later the fluids had separated --- clear at the top and purple at the
bottom. There were still a few bubbles on the top part. That didn't make
sense --- the purple silicon is now on the bottom and the DOT 4 on the top
has suspended air bubbles. Could the DOT 4 have sucked the color out of
the silicon? It is known for absorbing stuff like water.
New experiment: 1/4 inch of purple silicon and 3/4 inch DOT 4, then shake
and let set. An hour later, top 1/4 inch is nearly clear and the bottom
3/4 inch is light purple. Conclusion: silicon fluid floats on DOT 4 (just
like I was told) AND DOT 4 absorbs color (I assume its a dye) from silicon
fluid. Also --- DON'T SHAKE THE SILICON!
When the car gets back from the painter in two weeks (I hope) I'm going to
follow the advice of those who have successfully converted with minimum
effort.
Thanks to all who responded.
Nelson Riedel
Granville, OH
76 TR6 (at paint shop)
68 TR250 (next project - new paint)
70 TR6 (all the parts in a pile ready to assemble)
///
/// triumphs@autox.team.net mailing list
///
|