Change the oil, while it's draining, see what comes out. Usually as a rule the oiling system runs higher mean pressures than the cooling system. So, oil in the coolant is more frequently seen. Drain and flush the cooling system, use a mild detergent. Benzmac suggested "Shout" to me a while back. Have your compression checked. See if it recurs. Also, if diagnosis remains obscure, have the trans cooler tank in the radiator pressure tested. They can leak.
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.