What could be the source of a high-pitch whistle that comes with long trips? on 2006 Dodge Grand Caravan

The whistle only starts after driving several hundred of miles at a time. Also, in extreme hot temperatures. Other (most) times, there is no whustle at all. This has been going on for two years. It is coming from the back of the vehicle. I assume it involves the fuel system, but I don't think it's the fuel pump.

Asked by for the 2006 Dodge Grand Caravan
1 answer
very poss the fuel pump itself. have it diag and get est,hard to help without hearing the noise