[mgchevyparts]

The "brake" light comes on when ever the shuttle valve inside the prop valve moves off center. It can do this when either the front or rear section of the brake system has a leak. The valve moves in the direction of the low pressure to shut off the flow of fluid in that side. When you refilled and pumped it you recentered the valve and the light went back off. Do you recall which section of the master was low? That is the side that has a leak or some other problem. Generally the front bowl is front disc brakes and the rear bowl is the rear drum brakes. Also notice that the larger bowl or reservoir is for the disc brakes and the smaller of the two is the rear drum brake side.