My 2007 has 91K on it now and I start it every day, change oil every 4,000 miles. Just recently have noticed a new noise that sounds like a moderate grinding humming noise. Not really sure what it is, I bought a stethoscope and did some listening around with it in the belt tensionor, water pump, alternator, ect, and can't pin point it. Can really hear it when I put my ear to the radiator, but not really when over top or underneath. Any ideas?