I had this problem when I first got my 300D...this is one of the easier fixes I've had to do, literally five minutes. Stops that optional "external lubrication" of the engine from the droplets of oil that spray out of the crack in the hose. (Then, you can clean the engine and find where the real leaks are...)

__________________
1981 300D, "a lot of" miles (broken odo)
"Engineered like no other 24-year-old beater in the world."