Advice needed on brake fluid issue

[14kmtnman]

I was helping a buddy bleed the brakes on his GS 800. When I popped off the front master cylinder cap, it looked really weird on the inside. It appeared to be full of white mold. Part of it was soft and squishy and part was hard (same for the back cylinder). The hard stuff was hard enough to act as a splinter. We were pretty surprised and forgot to take pictures. But when we got to the rear brake, I got the below pictures. I spent 15 years in Seattle (very wet/humid) and never saw anything like this on my vehicles (cars or motorcycles). The GS is in the so called desert of eastern Washington and doesn't get ridden much, but is stored in a garage. After bleeding each port many times, including cycling the ABS, we were getting clear fluid out. The old fluid was somewhat cloudy with no white chunks present during the bleeding process. Is this a reaction to a wrong brake fluid type being used and or condensation? Or is this internal brake line failure? Or something else?

See the white layer inside on the bottom?


Looking down into the cylinder


after being dug out and put in a bowl

 

[cyclemike4]

I have seen real old brake fluid turn into some sort of grit that looked like light colored sand. I have also seen diesel fuel do the same thing. Not sure what the chemical process is that causes that but it does happen. If you got everything cleaned out and the brakes working you did a great job. Ride and have fun.

 

[robp]

Aluminum oxide corrosion ???

 

[2daMax]

Seems like precipitation of some sort. Never quite seen anything like this on brake fluids. Could be too much moisture reacting to brake fluids. They turn cloudy when mixed with water and overtime, precipitates into solids.