Water Pump Leak-3.9 Diesel

[Yogisailor]

Hey there gear heads,
Who out there knows their 3.0 TDI front to back? Just took off a leaky water pump. The pump has 10 screws, well I took off 11~

In the what I will call the valley of the water pump there is a bolt thats exactly the same as the other 10 and it is holding on a small over that has some rubber on the front and the center has a female threaded nut for lack of a better term. Well when you take this off the plate pops off. I put it back on and now its leaking coolant, or maybe thats what was ALWAYS leaking coolant.

My issue is I can not figure out what the hell to call it, so I can figure out what it is. Ive searched the web for an engine break down and gone through the engine schematics to no avail.

Anyone can help me out let me know!