Is the carpet wet or any other clue then mate? Are you loosing water from the system possibly? You can always bypass the matrix first before digging around under there. Just loop a bit of pipe onto the hoses where it goes into the bulkhead behind the turbo. B&Q do a perfect bit of copper pipe in the plumbing section... costs a couple of quid if that.

Behind the bulkhead this is all it is regards the matrix itself.



and this is the job in hand...



One of the pipes comes up along the engine from the pump and the other appears from behind the block.