I'm trying to troubleshoot a Powermaster system. The car has sat for a little while. When it's first cranked up the brake light stays on. I checked the brake fluid and it was good in the reservoir closest to the fender but very low on the side toward the engine. I added some brake fluid, cranked it back up and the light went off for a while but then came back on without touching the brakes. The pedal travel seems normal and stopping power is adequate. I turned off the car and then the fluid from the master cylinder overflowed. I pulled the cap off and the one reservoir that was very low before was milky and seemed to be full of air. I've looked at some troubleshooting diagrams on gnttype and other sites but am still not certain where to start.