My new leaking pan and gasket are on my E58 360. I had mechanic install it and it's leaking bad. I was told that the end gasket goes on the bottom of the side gasket at rear, and on top at the front, and maybe the mechanic did that wrong. The other suggestion was to buy a Superformance gasket as they are very high quality. I've yet to pull the pan myself and give it a shot, so I don't know how the end gaskets went in. I can see plenty of sealant though. The 360 and 318 use different pan, but maybe some of this applies.

I think it was RapidRobert who gave me the placement of the gasket tip and Scratchinfortraction the gasket tip. They are reliable sources