Our '05 VW Golf had been having a problem of continuing to lose coolant over a period of time. It would be find for a couple of months and then the warning light would come on. It was a mystery as to where it was coming from as there was nothing that was obvious anywhere on the engine and nothing on the ground underneath the car when it was parked. So, we turned it over to Mark, Stanford the staff. They ran a pressure test and finally detected a leak where a fitting connected to the engine block. So, the problem and mystery was finally solved!