I would go back and take another look at the heater hose and the nipple that comes out of the back of the head. It is held in place with a clamp and uses an o ring for sealing. Under pressure, that may be your culprit. try this. Get the motor up to temp, making sure there is adequate coolant on board. Remove the air filter box and get a flashlight and the "mirror", and really poke around. I'll bet you'll find your leak back there. Do this with the engine running and the heater off and then on.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.