1987 560sl rear brake bleeding
 

I have read that when bleeding the rear brakes, that the key needs to be in the "on" position-something to do with the a.b.s. system, and I have also read that the key does not have to be on. My problem is, I replaced both rear calipers-they were original, and I can't seem to get the brakes to bleed, so I'm driving on front brakes only. I bled tried to bleed them the 2 person method, making sure the reservoir was over full, but no luck getting them to bleed, when the brake pedal is pushed down, the rear brakes do not even move!
Searching links did not reveal any solution, so any help is greatly appreciated. Key on, or key off?

Thanks,
-DDaymen

Realize there are 2 chambers in the master cylinder that must be full of brake fluid for the braking system to function properly. Make sure the rear chamber is full of brake fluid.

Best to use a pressure bleeder which will keep both master cylinder chambers full and avoid introducing air into the system. Bleeding sequence is RR (right rear), LR (left rear), RF (right front), LF (left front). Be sure to bleed all 4 calipers and keep both master cylinder chambers full as you proceed with the 2-man bleeding process.

Well, it seems that having the key on made some difference, something with the a.b.s.? anyway, after that they bled just perfectly.
Does the key being on activate some part of the a.b.s., thus allowing fluid to flow to the rear? or just coincidence.

Thanks,
-DDaymen