Sorry Pardec, we can help you but you've got to help us help you, if you see what I mean.
Your TD4 has an oil leak. Okay, now is it engine oil, gearbox oil, IRD oil, brake fluid, or power steering fluid. You say its at the engine bay so I' go as far as discounting differential oil. You see the problem? Right, have a look tomorrow and try and determine where the leak is coming from. Ideally post a photo if you can. There is a good bunch of guys on here and between us we've seen most things on the Hippo. Once we can see your problem then we will do our best to advise you on the best course of action.
Please also supply any other information about the vehicals past, such as any mechanical work that has been done, any other problems you might have observed etc. Also, if you adjust your profile to show us the area you live in then we maybe able to assit in the best places to get parts etc.
Best Regards, Dave