I have a weird intermittent problem with my brakes over heating. It has happened on two events that I went to last year. First time (new Cruiser owner of a 1994 FZJ80) the brakes went to mush after a long drive decent down a mountain. I looked at the fluid and it was dark (maybe burnt?). After cooling all was okay for the drive home, and for the rest of the weekend. I had someone do a passive drip flush of the brakes a week later. Then I went on another trip. I did get some mushy brakes after a long decent, but not as bad as before. The fluid did turn dark again. I am thinking I need a power brake flush with DOT 4 fluid. Any other possibilities?