Yup, just as it stops dripping...another drop is allowed after 15-20 seconds.

http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/148937d1534934043-1963-om621-diesel-timing-db.jpg

The size of banjo fittings and hollow bolts should be as on om621/615/616 etc.

...Or you're talking about the injector return line fitting

https://i.ebayimg.com/images/g/14sAAOSwEjFXeXj~/s-l500.jpg