I had an odd experience bleeding the brake master cylinder of the 83 300SD from bone dry. The two aft ports bled normally but just a trickle of fluid from the front port. I hooked up the aft ports to the brake lines then the front port bled normally. The brakes feel fine. I can count on one hand the number of brake master cylinders I've bled but I don't recall this nuance in the past.

Sixto
83 300SD