cracked head/bung

hi guys,long time since I've been here....I've a 2003 td4 pre face lift....I've attached photos..got home last night to find no coolant in header tank...gad a quick look with torch and found the leak in photos..firstly the car didnt over heat and needle didnt rise above mid point at any time.....any body seen a leak from the bung/cylinder head on the right hand side of engine,behind/just below the egr pipe...any advice on what the bung is, is it terminal? am I looking at cylinder head? replacement or can it be filled with metal putty?...thank you

Looks like a freeze plug has corroded through. It happens sometimes, especially on engines that haven't had proper coolant changes, or on odd occasions rust from the outside on engines that don't leak oil.

Replacement is easy enough, finding the replacement plug might be the hard part.

So I just found the exact same problem on my 2004 TD4 auto this morning. I'm struggling however to remove the EGR Cooler in order to get to the plug. Rave-lr mentions 3 bolts but for the life of me I can't seem to find the one at the back. Any advice please?