That engine holds air forever.

Best way to bleed is to squash the upper radiator hose down, then crimp the small line going to the tank shut and release the upper radiator hose. This will suck a bunch of coolant into the engine. Repeat, filling the tank as necessary, until it won't take any more, then start engine and stand by for the thermostat to open. Tank will suck down, keep adding coolant.

You won't get the whole amount in, but for a flush who cares? When you fill with fresh coolant, expect to have to top off a coupe times over a week or so as the air works out. When the heater core stops gurgling it's full.

The other option of filling through the upper radiator hose works too, so long as you don't pour in too fast so the air can get out.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!