How much oil is in there?
if its got just the tiniest amount (say from a previous HG failure) oil will always rise to the top as its less dense than water.
I'd do the relavant tests to make sure is HG failure as the F4r is a bloody strong engine and HG failure is rare.
Im just wondering if it was actually done first time or just bodged!! I was thinking it would probably be cheaper to buy another engine that's had all the belts and stuff done! But would have to swap my cams over!!
Renault say they should not be skimmed. If it needs skimming its scrap.