Interesting thread.
My 2003 4/4 has the Ford 1.8 ‘Black top’ Zetec engine.
The expansion tank fitted (from a MkI Ford Focus) has a lower section marked with a Min and Max level; so very easy to check levels.
Filled to the Max level would still leave 75% of the volume of the tank remaining empty, when cold.
No problems; other than the tank once leaking from a weak seam. (Local Ford dealer supplied a replacement tank for £23).
However my 4/4 suffers very slight and occasional incontinence from the bottom hose connection, to the Mulfab Al radiator.
A problem that I’ve never managed to completely solve.
Bud
4/4 - Stanley
Double jubilee clips with the tightening screw at 180 deg to each other...that'll sort it