I live in the California "low" desert and I and some of my friends have noticed that the brake fluid in our vehicles turns black, or very dark, over a period of about a year. Anyone have any reason why this might be taking place?
Harry Truman
To me it sounds like condensation is getting in the system and what you see is mostly rust. I would be inspecting those master cylinder covers and flushing those systems.
The conventional wisdom on brake-fluid darkening, say a burgundy rather than the chardonnay color it has when new, is rubber deterioration, releasing microscopic particles into the fluid. This is something one might imagine being worse in a high-heat, low-humidity environment. Of course, if there is significant water in there, rust might be rearing its ugly head as well.
Water contamination at low levels is not supposed to be detectable with the naked eye -- methods include a refractometer, chemical test strips, or a machine that tests the boiling point. Or you can just do it as timed maintenance every few years (more for critical applications like racing) or after water contamination. Even a brake system in good shape is said to accrue a few percent of water content a year just from the ambient conditions (one thing that's presumably happening slower in the desert, but it does happen), so by the time the stuff turns dark, it's probably coincidentally time for a change due to water absorption anyway.
High levels of water contamination turn it a milky color, but you're probably not seeing *that* in your car unless it's been in a flood or something.
Cheers,
--Joe
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.