Three are other factors. One situation I've come across over the years is the elctric fan that cools the radiator starts to wear which in turn causes it to stick. This fan due to it's location takes a real beating. Splashing, dust, bugs, and everything else. With a duel fan system, it can be one or both. Start your car let it warm up and observe the fan/s operation. If not this I would look into the relay, which is the second leading cause of overheating in my experiences, if you check this, and its not the case let me know

