[Richard230]

Yesterday I replaced my brake fluid for the second time on my 2011 B5.  I think I will do it more often from now on.  The fluid looked OK when seen through the reservoir window, but when I opened took off the lid the fluid was looking kind of grey and the inside of the reservoir seemed to be coated with a grey sandy material, like the fluid was dissolving the pot metal material. Also, the paint on the outside of the reservoir was flaking off and it looked like the entire reservoir was corroding, both inside and out.  What do they make those brake reservoirs out of?   

Anyway, I drained the existing fluid out of the system, used a screwdriver to scrape out the inside of corrosion (or whatever it was), wiped out the inside of the reservoir, then refilled the container and started flushing the system through the caliper bleeder, which produced a strange "sandy" sound as the old and new fluid passed through the bleeder.  I have been servicing disc brake systems since the 1970's and I have never seen a brake master cylinder made of materials like the "+pricol+" components installed on my Royal Enfield.  Where do they get this stuff?   

Fortunately, my brakes still work just fine, but I really am concerned what that grunge in system is doing to the insides of the master cylinder, brake hose and caliper components.  I think I will start replacing and flushing my disc brake system every year from now on.