I can't access the M104 FSM so I can't speak for that and the M103 chapters on startek (W201) seem to be missing the description of crank case breathing...

...the M102, however, seems to have a conventional crank case breathing system.

I don't see how they can create a vacuum without some sort of mechanical device if they don't use a venturi - so OK I guess I'm a bit restricted in knowledge on this subject but I've only come across vacuum being made in an automotive context by either a vacuum pump or air flow through a venturi.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!