Coolant leaking vw Passat 1.6 1999 heat on with fan, window fogs.

is the floor board on passenger side wet???If yes it's the heater core, which should be accessible by removing the glove box. Did u check the oil, to see if it 's milky??? some times on the vw of any kind, they spring a slow leak on the head gasket which could cause the abnormal starting in the morning. Which then, as the engine warms up causes the gasket to swell up and seal itself untill the engine cools completely off again. Eventually the gasket will completely fail and u'll have to bring it to a shop or get a repair manual to replace the head gasket.