Can anyone help me pleease?

Ok,
My heater marix went in the caddy back in March and i managed to swap it over.
Back then i had the usual signs and was able to establish that this was the problem.
Last night i was driving back from a friends and the windows began to get a bit steamy. (no pun!)
I put the blowers on hot and it became worse.
The smell of radiator water became very strong so i opened the windows.
The water level is ok.
Oil levels fine and she sits at the normal temperature.
My passenger footwell is bone dry.
I am totally stumped as to what this may be and any help would be gratefully appreciated......please help!

Any damp things in the van mate?

Check the pollen filter area in the bay. Possibly water getting in and settling inside

Nah, nothing damp in there, i wish it was that simple pal!
Ive checked the pipes going to the marix and theyre all dry. When i put the heaters on full heat the cab is almost filling up with steam which smells like radiator water
I have a horrible feeling it may be the matrix again

Look in the scuttle area mate. Maybe water getting in via the filter.

I'd of thought you'd notice a drop in water if the matrix was leaking. Feel the carpet

It could be the matrix because if you are getting steam the water is being dried off by the heat
Get the cooling system pressure tested , that should find the leak when its cold

Thanks cor the help guys. Im completely stumped by this! No tale tale signs at all, no damp floor, no water gettin in around the pollen filter housing, i have no idea! If it was a hole in the matrix surely i should have some moisture somewhere as water would be constantly pumping around wouldnt it?