White smoke is a sign of low compression OR a bad head gasket.

Does coolant slowly disappear from the reservoir? If so, expecially if you also have pressure in the cooling system when it's cold (before starting), you have a cracked head and will need to replace it before it hydrolocks and you bend some rods.

If not, do a compression check and leakdown check -- this engine will use oil if you have bad cylinders, so if you don't have oil consumption problems, it's likely a valve problem if you have low compression.

Dead hydraulic tappets can give you low compression, too.

If you have serious injector knock on that cylinder, you may also have a leaking pressure valve holder in the IP.

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!