Sounds like a blown head gasket. Be sure there are no air pockets in the cooling system. Be sure the cooling fans come on. And obviously the coolant is full. After the basics are covered than we can suspect other things. Take off the oil cap and look on the inside of it. If the oil looks like a vanilla shake than theres your problem. The head gasket has blown and there is coolant in the oil. The head gasket will need to be replaced.