[SpeedTherapy]

These motors have a clutch fan that will sometimes engage when first starting out for a short distance. They make a lot of noise. For the most part, it will only engage when airflow through the radiator is insufficient to cool the motor. Duramax, huh? Anybody with this engine has to check out this forum: dieselplace.com. Sit back, read, relax, spend money, go fast.