I have a 2003 Mitsubishi Outlander. About two months ago, I replaced (myself) the radiator fan because it had stopped working. I bought the new fan on the internet and it was fairly easy to install. It was a little louder than the original fan, but it worked great. Last week it suddenly became louder and stays on for a minute after I turn the car off. Is the fan defective? Should I return it? Should I ask my mechanic to test it? Or just ignore it?