Without the thermastat being changed in so many miles, that is where I would start, and while you are doing it flush out the radiator and cooling system before putting a new thermastat. That would remove other gunk in the system that could slow down the circulation. The fans could be the problem but would start with cleaning the system first. With driving at highway speeds there is just enough circulating to keep it cool.
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Sunday, June 14th, 2009 AT 11:36 AM