At 04:31 PM 12/28/02 +0100, Hans Duinhoven wrote:
>.... how often I should renew silicone hydraulic fluid, ....
Since you have a vented reservoir on the master cylinder, at least every
two years, or just as aften as any other fluid, and for the same reason,
because of moisture in the system.
The silicone fluid doesn't absorb moisture (not much anyway), but that
doesn't keep moisture from getting into the system. When the reservoir
breaths it introduces changes of air, and temperature changes cause
condensation (especially in humid climates). While other fluids might
carry a moderate amount of water in suspension, the silicone fluid
doesn't. Instead the water settles out in droplets or puddles in the low
parts of the hydraulic system, often in the bottom of the slave cylinders
where it causes corrosion to the cylinder walls (or iron pistons in
calipers), and in low spots in steel brake lines where it can eventually
cause rust through.
This doesn't make silicone fluid any worse for corrosion, just makes for
more local corrosion spots rather than all over the system, and you still
need to flush it occasionally. Aside from not eating paint if it leaks,
silicone fluid is a nice preservative for rubber hoses and seals, so if you
treat it well you might never have to rebuild the hydraulic system again.
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
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