Block drain is on the rear of the block, down low, more or less behind the exhaust manifold on the passenger side. Very nicely, there is a hose nipple on it so you can direct the used coolant into a bucket or empty antifreeze container instead of all over the floor like on the older engines.

Fill completely with water and drain a couple times will be sufficient if you are just changing coolant. If you do the citric acid flush, you need to circulate both the flush and the rinse with an open thermostat, else you will have corrosion problems from residual citric acid.

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!