We need a bit more info in order to help you out... Is the sound possibly coming from the fan? Has the temperature been a bit hotter than usual where you live? (Your profile didn't say where you live.) Is it constant or sporatic? Does it go away after the motor has warmed up? Is it coming from the engine compartment, wheels, front, rear, etc... Do you hear it more when you accelerate? Please elaborate and we'll see if we can throw out some ideas. Thanks,
John