[shorod]

When you say the fronts will not bleed either, are you suggesting you are getting air and fluid all the time, or are you getting nothing from them? How far are you opening the bleeder screws, and how are you bleeding them (Suction bleed, 2-person, speed bleeder screws, etc.)? Since you mention a cylinder coming apart, I suspect you are peforming a 2-person bleed. Has the team bled brakes before so the person pressing the pedal is announcing when they are nearing the floor and the person at the bleeder screw is closing the bleeder and ensuring the bleeder is closed before the brake pedal is released?

On the driver's rear are you saying the wheel cylinder is coming apart? Why don't you have the brakes assembled and the drums installed to prevent the cylinder from coming apart? Have you tried removing the bleeder screw to see if you still have issues with the wheel cylinder coming apart? With the bleeder out basically no fluid should make it to the wheel cylinder (path of least resistance).

-Rod