I removed the oil pan of the 300TD at about 150,000mi.
It was extremely clean. I removed it to replace the turbo oil drain tube O ring and to replace the oil pan gasket. After 150,000 miles of using "dino" oil and Mercedes filters, I did feel that the oil pan was quite clean and found no particles or gunk in the system. I try to change the oil at 3-4000 interval and always with a new Mercedes filter.
Your lifter is bleeding down once the engine is off. Its probably a mechanical condition in the lifter. Probably not dirt blocking the oriface of the lifter.
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car