Very early in the life of US CRD's some dealers fixed the air in fuel issue by replacing the fuel lines. Having seen the "O" ring connectors when putting on my lift pump I think most of the air is entering there. Granted the filter is the high point of the system and is where the air collects and without fuel in it the heater connection will melt. I had air in fuel on the ride home from the dealer the day I bought mine new. The fuel lines on a CRD are the same as a gasoline engine that are under pressure not a vacuum like ours stock. Ours stock are under a vacuum and diesel is heavier to lift then gasoline. Doomed to leak
My two cents
