An old speedometer cable in a drill, variable speed is best, ream out the hole. You have to get all the way into the intake, since that is were the oil is coked from the hot exhaust gas.
Probably best to remove the intake, so that you don't drive chunks of crud into the cylinders....expensive damage will result!
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!