HELP !! Weird Coolant leak

[Dervman]

Stopped to fuel up and get a Car Wash in the SDL and was towelling it off afterwards when I noticed some coolant running out from underneath. Stopped engine immediately although I checked first to see temperature was still at normal. After stopping it still dripped a bit but not much. Checked all the obvious things under the hood - hoses, Expansion tank level (normal) and water pump (OK). Nothing seemed wrong. There was evidence of coolant that had dripped out of the large drain that comes through the bulkhead into the back of the RH Front wheelwell and I also found that a small amount had dripped onto the RH Front passanger floormat. I assume this was from the heater vent but it didn't seem wet when I checked it.

Started engine again but only dripping appeared to be from the A/C evaporator dripping around the transmission tunnel (is that right?) as the fluid was just clear water with no coolant in it. There were no further leaks on the short drive back to the offfice or after I parked and fluid levels and temperatures were normal.

Anybody got any suggestions ?? My first thought is the Heater core because of the coolant on the floormat but now it seems to have stopped.