Nissan Repair: excessive water problem, nissan primera, excessive water

Question
1996 nissan primera 1.6 lx 141,000 miles, new radiator, new battery, new brakes and new alternator all within the past month.  Drinking 7ltrs of water in one week.  Unable to find a leak from the radiator since the new one has been put in but now it's drinking like a fish.  Every couple of days it takes 2ltrs.  Have tried not to use the heater but this hasn't really made much difference either (it was suggest that the heater matrix was the cause).  Please help.
Many thanks

kerry

Answer
Hi Kerry,

This is the second one of these that I have had this question for. I wonder if there is a common problem. I would look in two places. I know you have looked under the car, but look in the floor on the passenger side and see if the carpet is wet. Second, is there any white smoke coming out of the tail pipe?