black brake fluid

[seattle7]

After every race weekend, the brake fluid in the reservoir turns slightly dark (black). It seems to get worse as I let it sit. Could the brake fluid (Wilwood 570) be attacking the seals? There is a small leak at the reservoir seal into the master so this is the suspect.
Car is an '86 2nd gen. Last winter I rebuilt calipers, installed new master cyl. and put in Goodridge SS flex lines. Everything else is original. I bleed before every race weekend. My first thought was water or air contamination, but when I bleed I get no bubbles, and when I race I don't get any noticeable fluid fade.

Thanks,
Mike

[zracre]

you need to change out the fluid in the resivoir regularly...also excersise the calipers when you bleed them (compress the old fluid out of the calipers)and always start with fresh fluid.

[tom_sprecher]

Dark fluid at the caliper is usually from overheating the brakes. We changed to Motul once about 3 years ago and never had a similar problem since.

Dark fluid in the master is usually water contamination and a normal bleeding will not remove it. A flush is necessary. Next, figure out where the moisture is coming from.

Good luck,