Spit64,

I have an 87 300e with the m103. M103 and m104 are VERY similar, and have almost identical oil leak issues. Typically, oil will leak from the front timing chain cover, the FRONT and REAR of the head gasket on the PASSENGER side, the passenger side of the valve cover, and sometimes from the oil filter housing, which is what you might be seeing on the drivers side of your m104. The oil pans almost never leak, but anything can be possible as our engines rack up age and mileage.

Hope this helps