My car overheated on the side of the road. We let it cool for two hours and then drove it again for about 10 min. before it died on its own. This morning I cranked it up and drove it 10 min. more. before it shut off again. (I am trying to get it to a mechanic). It stays cold for about 3 min and then is at the middle mark for about 5 minutes, then quickly goes to the hot mark and shuts itself off. There is no smoke or water boiling. The water looks fine no obvious leaks or hose problems. What other things could this be? Thanks in advance.