crack in engine block?

[MaurizioG]

In the end it was nothing wrong with the new head but a real tiny leak of coolant dripping from a crack in engine block above oil filter and oil pressure bulb, very near below is a core plug (freeze plug?) but it was not leaking from it. So far I stopped this leak/crack by using a USA product that I poured into the radiator (have only used 1/4 of the bottle). I don't know how long this fix will last despite in the bottle it says permanent fix. I don't know the forum rules so I'm not writing the name of this product.