Seeking assistance with part Identification / Cooling system leak
 

1996 Buick Regal 3.1-liter V6 engine
developed a leak in the cooling system.

Beneath the engine, behind and below the starter, off center toward the passenger side is a
rounded rectangle shaped pan or cover, approximately 4 x 7",
In it are four holes laid out in a square pattern, roughly 3" hole to hole

The leak come from 2 of these holes.

It appears as though it is held on by only two bolts but i found that the removal of these two nuts alone do
not release it. I don't know if its held on by something else or simply rusted in place. I did not want to force it until i learn more.

I'd very much appreciate if someone could identify this part or
direct me to an engine diagram/exploded view or similar that might include it

Thanks for any help in advance.

https://cimg1.ibsrv.net/gimg/www.bui...2ebdf9f459.jpg