My Temprature gauge has been playing up latley, dropping back to Zero then back to normal. I also noticed my water has been going down, topping up but still goes down to minimum after a week. I was thinking of changing the temprature sensor first, but talking to a chap who had an S3, he said he had the same problem, changed the sensor but still faulty, it was the themostat?? I cannot find where my water is going?? I took the undertray off and run the car hot, but still cant find it,, although the tray shows a white water mark on it, on the front left side!!! anyone had this problem??