Thought all was going so well with my 2002 4.6 came home from work today and saw water around the osf wheel popped the bonnet to see water header tank empty! which i had only checked 2 days ago. refilled with 5litres!!!!! of oat+water removed air and left to tick over now the temp gauge does not move from middle never has since I've owned it and today the wife who did a short run in it does not recall any unusual temp or lights and no smells there is no mush inside oil filler cap and once up to temperature i can still squeeze top hose although there is definitely more pressure there when up to temperature I'm sure the water has come out of the over flow but why? HELP