coolant leak... help!

[snopro67]

I have a small leak underneath the drivers side of the radiator. The radiator has been replaced in the last 5 years so I am thinking it is ok.
It seems to be coming from the "leveling switch" at the bottom of the expansion tank.
Has anyone had experience taking that switch out of the expansion tank?
Is there an O-ring in there?
I don't see one on the parts schematic.
Item 13 on my attached picture.

[albudracr]

Just replaced the sensor in my boss' '02 540 because the sending unit itself
started to leak around the base of the terminals. It's fine now. Maybe in the drawing the #14 Oring is bad? Just a thought.

[snopro67]

Yes, I saw the o-ring on the schematic once I looked at it closer. Once I got the switch out it was bad also so I changed them both. (new sensor comes with the o-ring)
drain plug was leaking too,
Oh, and the expansion tank,
Oh and a loose hose clamp on the radiator hose that is beneath the expansion tank.
Oh and a leak from somewhere else that I haven't tracked down yet.
I might end up changing the f****** radiator before it is all said and done! :mad