Last couple of days, it's been in the 20s and I've noticed a noise that I can't figure out what it is. The sound is a "woooo" similiar to the sound you get when blowing across the top of a coke bottle. It comes and goes with a slight variation of the throttle. (less than 125 rpm). At first I thought it was wind but now I don't think it is. It seems to only happen when it's below 32 degrees. Any idea???
Steve
Steve