Re: [MV] Silicone Brake Fluid - Another PS

Alan Bowes (
Tue, 19 Oct 1999 13:20:56 -0600

I've read that the compressibility of a brake fluid can be directly affected by the
amount of "dissolved" gas in the fluid, although this does NOT mean that one will be
able to see the dissolved gas as "bubbles." I've also read that a silicone-based brake
fluid contains more dissolved gas than glycol-ether fluids, which supposedly tends to
increase its compressibility relative to the glycol-ether fluids (although I haven't
traced this reference to its original source(s)). I would think that dissolved gases
should tend to remain in solution under normal operating conditions (normal range of
temperature and pressure), rather than form visible bubbles.

However, if one does happen to have any obvious bubbles in the brake fluid, it is a
problem, because these bubbles can not only cause a very spongy pedal, which can be
dangerous in itself, but if the bubbles happen to coalesce into a large bubble at the
wrong place, it could cause a total system failure, so it's important to properly bleed
the system until the fluid is bubble free.


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