Oil leaking from plug in 380sl block?
 

I think I finally found the source of a mysterious oil leak from the engine of my 380sl. I was afraid it was coming from the rear main seal or the head gasket, because oil was dripping from the bottom of the bell housing just behind the grate. However, I replaced both of those over the winter, and the valve cover is dry.

As it turns out, and as the picture shows, there seems to be some sort of a plug on the rear of the left head -- just below the valve cover and to the left of the large bolt in the center of the head -- that's definitely leaking oil, slowly but surely.

I'm assuming and, hoping, that it's an Allen head with some sort of washer on it that can be replaced. So I was wondering if anyone here has seen this problem, and knows how to fix it.

Thanks in advance for any help anyone can give me.

P.S. The picture isn't showing up here, but it does on the message I cross-posted in the SL forum.

The system won't let you double-post pictures.