I have an X reg Mondeo (Mk 2) and have discovered water under the carpet in passenger footwell. I have checked and sealed the pollen filter housing so its not coming from there. I am suspecting that the (2 plastic and 1 rubber) grommets in floor pan are the culprits.Perhaps they have aged and contracted letting water past the seal. I just can't think where else the water is coming from.Its definitely coming from underneath car and not from the top down as I have rubber mats.I am going to dry it all out (the insulating felt is sodden and stinks like hell, which is why i looked under carpet in first place!) and smear loads of silicone sealant over it. The air con has been switched off and can eleminate any blockage in drain hole. So I don't think its that. There is a lot of water so I don;t think its the air con. Has anybody else had problems with these stupid grommets ?.

Have a look at the drain holes in the underside of the door, I had this problem with my 04 Fiesta during a particularly rainy patch, if the drain holes are blocked the water will find a new way out, between the door and the door card.