This is the 3.0 litre V6 Duratec based engine that has been used in a wide variety of cars including the Ford Mondeo ST220 in Europe and the Ford Escape, Mercury Mariner and Mazda Tribute in the USA.
I don't think this is a pure sealing cap as it has a "blow off" mechanism inside and appears to be set at 1.2 bar. It looks the same as the Ford OEM cap judging from what I've seen in the Ford Escape workshop manual.
It runs with a Sifab radiator and has never had a cooling problem although it can run slightly hotter at times which I think is down to the cooling coefficient of the Evans Waterless coolant it uses but that is a different conversation. (It had Evans Waterless in when I bought the car)
