I notice that my truck (a 99 GMC 2500 w/ a 7.4l 454) runs at almost 210,a little over, when I idle for long period or I am parking my 5th wheel. Once I give some gas and get going I hear the fan (I call it the jet engine). I do not hear the fan in idle. Is there anything wrong? I'm thinking clutch fan or relay is not working.