humming noise from the back

[JudgeM]

Hi All,

For all this time I;ve been hearing this humming noise, I thought it is the radiator fan. One day however while standing outside, I heard it louder from the rear of the car. Its a noise that comes on, then goes off. hence why I thought it was radiator fan.

Is there some pump or fan or something in the rear of the car that only comes on sometimes ?

[BLH]

Probably hearing the fuel evaporation leak test pump.
My manual indicates a test is done about five hours after turning off the car.
The hum is probably you hearing the leak detection pump turning On for several minutes.