> Silicone is DOT 5, and not compatible with any other brake fluid.
Actually it is "compatible" (the DOT 5 standard requires it), it just
doesn't mix with them. Any DOT 3/4 remaining in the system will stay
separate, and continue to deteriorate; eventually winding up as a tarry goo
in dead zones (like the bottom of the slave cylinders).
The goo is ugly, but at least in my experience, relatively harmless. I
haven't seen any evidence that it was continuing to corrode the alloy slave
cylinders or interfering with operation in any way. One curiosity though,
it sucks all the purple dye out of the DOT 5, leaving it nearly clear.
I did my first DOT 5 conversion with flushing the lines and so on; but ever
since then I've just bled through until I get purple fluid at the bleed
valve. For example, I did that on a non-Triumph at 80,000 miles after one
of the front calipers had started to leak and been replaced. The entire
remainder of the system never got touched again and was still working fine
when I junked the car at about 250,000 miles.
YMMV of course. I won't claim it isn't better to completely tear down the
system, flush the lines and replace all the seals; just that in my
experience it is not necessary.
-- Randall
|