It is hard to comprehend what went wrong with the master. If the primary piston had somehow stuck / frozen totally, there would be NO brakes (front or rear) but still a firm pedal. The rear line pressure is derived from the primary piston (toward rear of car) pressing on the "floating" secondary (for rear brakes, front outlet) piston. So if the rears were working, the primary piston HAD to be operating OK. Bizarre. I'd love to dissect that master.

Before...I was thinking stuck w/cyl pistons...

Rick