Bleeding brakes, but no pressure

Hi Everyone,

I removed, cleaned and re-installed the brake fluid
resevoir on my 88 300e and refilled it with dot 4.
I then had my father pump the pedal to build
pressure and bled the right rear caliper. All the time,
being careful not to let any air in the system.

But when I tried to bleed the left rear, all I got was a mixture of
bubbles and fluid. I continued to bleed it, but now
I'm not getting anything. Not fluid. Not air.

I can't seen to get any pressure in the system. I've
tried running the vehicle for a minute or two but I still
have no pressure. The pedal stays spongy.

I've tried a gravity bleed, (10 minutes ) but not a drop.

Am I doing something wrong?

I've done a search on this and nothing seems to
apply. Any insight would be appreciated.

bluebenz