To check chain stretch, rotate engine until the right camshaft alignment mark and the mark on the cam tower are matched up -- nominally TDC on the crank. Look down and see how many degrees the crank is after top dead center -- this is the chain stretch (wear) in degrees. Less than 8 degrees is fine, more, replace the chain.

If the chain is sloppy, the tensioner is leaking down and should be replaced or repaired -- the internal o-rings are shot. Not too hard to do, it is under the alternator below the head on the front cover. I'd fix it, a slapping chain can break the upper guide, and that usually gets in the chain and breaks that, bends the valves on both heads and costs $$$$$.

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!