Deep hollow clang clang clang at engine speed is a spun bearing, probably #2. If allowed to go, the crank will soon score and break.

New engine time. New engine time anyway, as the bearing cap and block area are chewed up.

If loosening the injector cap nuts one at a time (then retightening) makes the sound go away on the affected cylinder, it's an injector.

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!