I bought my A2 less than two weeks ago from a garage, I've driven it about 250 miles and when I parked up today I noticed a trail of liquid from where I had reversed into the drive and when I checked underneath the car there was a steady drip coming from the underside near the front of the vehicle but not directly under the engine. It continued dripping consistently a long while after the engine had been off. I have taken the bonnet off and can see no visible signs of leaking from that angle and I have tried starting the vehicle again to see if I can see anything happening whilst it's running. Strangely enough the dripping seemed to slow whilst the engine was running and when I turned it off again, whilst the bonnet was off I heard a hissing sound from the engine which stopped after about 30 seconds to a minute. I also noticed whilst the engine was running that the coolant/water seemed to be bubbling almost. At no point has the temperature gauge on the dash risen above normal temperature and the water level remains the same as it was when I bought the car. There is no white residue amongst the oil on the dipstick either. Can anyone suggest what this could be please?