Gauge shoulod be acurate since the last time I drove it,it was defenatly overheating when I got it home.Brake drag is a possibility,but it is not noticable when driving the car.The heat seems to work fine,have not noticed any odor in the cab.The car is running on 100% biodiesel,mwhich it was not when we bought it.Thanks for the ideas,any more would be helpful.