I have a similar problem to PHB except on an Audi A6. While I was away last week a mechanic took a look at it and said it was a leak at the water pump, and he would advise that the water pump be replaced and as the car had 85000 miles on it, he would advise getting the timing belt done at the same time. Because I was only there for a day, he was not quoting for this job, but I will see about it this coming week and let you know what the price quoted was. In my car's case, I could see wetness at the bottom of the engine lying on the cover at the floor.