The problem with the single reservoir master cylinder is that it is very dangerous. THe factories all realized this as cars were evolving and changed it. Yes, they work fine. Until they fail. There is NO backup. Modern dual reservoir master cylinders are dual reservoir. In other words, they have two tanks to hold fluid. If there is a leak somewhere in the system, there is always a backup. With the single reservoir master cylinder, a leak anywhere in the system results in pedal to the floor, and zero brakes. None of the factories ever used the single reservoir master cylinder with disc brakes. Ever. Yes, it can be done. Yes. It works. But it is not safe.
