A couple weeks ago my newly rebuilt engine developed an oil smell and just a drip or two on the cross pipe. Using info from this forum, plus a flashlight and mirror, I determined that the oil pressure switch (sending unit) was the culprit. I could see oil weeping out past the plastic.
Engine drop, I thought. then I thought again.
I got the part from our host, a 24mm deep snap on socket from ebay, and attacked the thing with a gorilla arm reach around.
I got it and guess what - no more leaks! Here's the offending part - you can see where it leaked :
and here's the magic installation tool - an old spark plug boot - just the right gizmo
this was a left handed job, totally blind, but it took an hour and a half. I felt the crush washer compress, and brought it up to torque just right.
Took it for a test drive and guess what - no more smell, no more leaks !!