Harmonic Hum from engine

[Farlow]

Odd sound coming from the engine. When at idle or when I let off of the gas, a harmonic humming sound comes from the engine. When I give the car gas or rev the engine it goes away, but the sound will return again a little later. Any ideas? Thanks.

 

[HoustonGT]

I have the exact same issue as you and have no idea what it is at all. Maybe someone can help us out

 

[StratGT]

This hum sound is something thats been listed on the boards before. I have the same problem. My car is a 2000GT. I think its the water pump, but others say it isn't. I've tried for 2 years to figure it out to no avail. Oh well.

 

[Farlow]

I have a 1997 GT and the sound only started a few months ago. It could be anything I guess since the car has over 120K on it. The only thing I can think of is the cold is making something loose?