My Tiguan purchased March 2011 has developed a small coolant leak - about 1/2 a teaspoon a day but not every day. But on one occasion when the car had been parked in our driveway facing downhill for three days my daughter took the car out and I noticed a large amount of coolant dropping from underneath when she backed up the driveway. It must have accumulated on the cross member or somewhere. I later checked the coolant level and found that it needed about 300 ml to top up. Since then it has been parked on the flat and either has no leakage or just a couple of ml and hasn't required any top up. Any advice on what is going on before I take it to the dealer to fix?