oil leak from unknown allen head plug

[mlozzi200478]

hello,i have discovered a weeping oil leak it is located above the alternater,on the front engine timing chain cover,passengers side.the piece leaking is a very large round plug type or bolt,its got a huge allen wrench fitting on it. the round head of this plug is approx 1.5" diameter,i do not know what it is or if i should tamper with it,i had previously cleaned all the oil off and finger sealed the entire area with rtv but im seeing the oil slowly seep from this round headed huge allen head plug,thru the rtv silicone. this is on a 1989 300ce,any ideas as to if there is a copper pressure washer behind the plug or bolt, or if it can be loosened and rtv applied behind it,then retightend.thanks everyone.marc