New Master Cylinder - CAN'T BLEED???
 

I installed a new master cylinder in my '86, 560SL and I foolishly didn't bench bleed it before installing. I have been bleeding it now about 75 times, using both a vacuum and additionally pushing/holding the brake pedal and I still have no pedal feel (it goes all the way down when pumping) and a load of air with some fluid comes out of the LR caliper. Yes, the reservoir is as full as possible.

I hate to remove the cylinder and start over again, but certainly will if that's the answer.

The car also has new rear calipers and rotors. No leaks anywhere I can see.

Suggestions will be greatly appreciated.

Have someone help you.Bleed the old way start at right rear have someone pump and hold while you bleed.Continue till clear fluid.Now left rear(drivers rear).Then Right front,then left.This should push the air out that got in.
If its still low pedal repeat or use stick method. Stick Method,wedge a stick,broom handle to hold brakes down while you go to bed.Repeat might take 5 nights but it does work.

You may very well have to bench bleed it before you can get it to bleed on the car.

Chuck it in a vise and fashion some lines from the outlets into the reservoirs, fill the reservoir and continue pushing the piston with a screwdriver until no bubbles come up. Then mount it in the car and remove the bleed tubes and connect the lines one at a time. You should then be able to bleed on the car.

You can do all that "bench bleeding" with M/C in the car.