Hi Dana,

I had the same problem with my 99XC. The leak was coming from the o-ring connection to the heater core. All you have to do is tighten up the screw that holds the black clamp on to the heater core and check for leaks. I stuffed the gap between the clamp and the floor with paper towels. After 2 months I have no leak.

Oh if the heater core was bad and leaking you would be getting coolant leaking from the heater core box. The heater core is mounted in a white plastic box that bolts to the bottom of the passenger cabin air manifold. If the heater core was leaking you would be getting coolant leaking from the seam where the heater core mount to the passenger cabin air manifold.

Also I removed the heater core in my car. I can never see a heater core leaking. Mine was built like a tank.

Good luck,

Steven---