At 01:29 AM 2/24/2000 EST, Rick Ewald (REwald9535@aol.com) wrote:
>
>I was in the parts business when silicone fluid first came out (early
80's). One of the concerns then was that air bubbles took longer to rise
to the surface and "pop" leading to a possibility of difficulty in
bleeding. .... Did you take any special precautions in the adding or
bleeding of the DOT 5 fluid?
Nothing special, just normal precautions. Keep any dirt out, and pour the
fluid slowly so as not to generate bubbles unnecessarily. I have for many
years used an EeziBleed pressure bleeder. This uses an external reservoir
(clear see-through bottle) that holds about 2/3 quart of fresh fluid. The
pickup pipe inside of this reservoir drops down to the very bottom of the
bottle where it is less likely to encounter bubbles in the fluid. Per past
experience, I have never noticed any bubbles in the silicone fluid that
were large enough to see.
The normal method of bleeding brakes (without a pressure bleeder) by having
one person pump the pedal while another works the bleed nipple has the
potential (though small if careful) of possibly introducing bubbles through
the back door. As the pedal stops moving and some fluid continues to
dribble out of the bleed nipple before it is closed, there is the
possibility of some air entering back through the bleed nipple or around
the threads of the nipple. Vacuum bleeding at the exit and of the system
also has the potential of introducing a small amount of air around the
threads of the bleed nipple. The pressure bleeder pushes the fluid through
continuously in one direction only under constant pressure, so no chance of
outside air entering the system.
The pressure bleeder also generally moves fluid along the line at a
sufficiently high velocity to carry any air bubbles along with it to the
exit point, even when the line runs substantially downhill as it does with
the hydraulic clutch. There have been times when when nothing else would
work to flush the air fron the clutch line except a pressure bleeder.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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