[DavidBetts]

Had this problem. I have Wilwood clutch and brakes masters, brakewise pumping to front Wilwoods and Jaguar rear brakes. Having raced the car, in August (102 degrees), the fluid turns black and eventually detroys the master cylinders. I changed damaged master, flushed and filled, all cylinders, with Wilwood High Temp EXP 600, now it would take temperatures up to 626 degrees to boil and fail. Also ceated and installed a heat sheild to redirect the extream heat from the headers. All has been well for two years now.
Good luck!