That could be the drain plug on the block if you are lucky but it might be a core plug...

Check along the length of the block under the manifolds - all of those bits are kind of between the manifolds and the starter motor solenoid.

If you still can't locate the origin may be taping (dry) toilet paper to the bits where you think the leak may be will help. You can easily see when this stuff gets wet!

EDIT - bog roll can catch on fire when it is dry!

__________________
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!