the brakes work great for about three months after I bleed them and then I will have to do it again. THERE IS NO FLUID LEAKING ANYWHERE that I can find and we took it to the dealer as the last resort and they said it was an internal leak in the master cylinder but would not tell me how they arrived at that. Anyone ever have this trouble before?

 

It's rare but air is thinner than brake fluid and so can get pulled into the system easier that fluid leaking out. The seal in the back of the master might be leaking in only one direction.

By now I'm guessing it's already replaced. Did it take care of the problem or what did you end up finding ??