Oil leaking from hole in Lower Timing gasket on 4jx1 engine

[Pogihan]

Hello everyone,
Im new to this forum and have just bought a 1998 Isuzu Plasair bighorn with the 3.0 litre diesel 4jx1 engine, and it was leaking a bit of oil. I have taken the radiator out and other bits and pieces and seemed to have located a hole in the lower timing case cover. I am wondering if i can just weld up the hole/putter fill it, or if it served any purpose like a breather.

There are protruding holes around near the hole that look like bolts go into them but nothing was screwed into them and the hole doesn't penetrate right through the case possibly half way. it looks like something has hit it causing the hole to go right through the cover. If any one has a repair manual or images for the lower timing case cover that would be very helpful thank you.

[geeves]

http://www.mediafire.com/?i36dwl1pkhb4g
is a link to the bighorn manual which covers this engine
There shouldnt be oil anywhere near the timing belt