There was another case of OM602 noise on this forum years ago that was solved by changing the two o-rings on the oil filter tube. Very strange. I don't think that noise cycled like yours, however. Cheap and easy enough to try.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC