My jeep is overheating. I have a 4.0 with an auto trans I have replaced the thermostat, water pump, radiator, temp sensor, and hoses. When I start driving from cold it goes up to around 250 and when I rev it up in neutral it goes back down. It will go up aand down but eventually stay between 220 and 230. I don't drive it because of this. What else can I do?