I have disc brake conversion, drum back, proportioning valve and dual reservoir master. Brakes are spongy, always have to do double or triple pumps to get pressure. I disconnected the back drums and plugged the master, and the brakes work great. Holds pressure, single pump, feels great.
so here is the the question, if the dual reservoir acts as two seperate systems, why wouldn't the brake pedal stay solid if even only the fronts where working? Isn't the point of dual reservoir to operate as two independent systems as a fail safe?
I understand that I have a problem with the back brakes, I haven't pulled the drums to check the wheel cylinders, but say a wheel cylinder has failed, in a dual reservoir why would I also loose the front brakes? Well not actually loose, but why would I need two to three pumps to get some kind of pressure.?