The M104 develops a characteristic weep at the front-right of the cylinder head from an oil passage that owners say should simply have been plugged; it is regarded as a nuisance rather than a threat. C43 cars show up with front timing-cover, oil-pan, and oil-filter-housing leaks that get resealed.
Front cylinder-head and timing-cover oil leaks
Mercedes-Benz C36/C43 AMG (W202) · mechanical