Left the truck running while I got out to talk to someone yesterday and heard a rhythmic pulsating whirring noise.
Initially thought it was the noisy ac system and didn't pay much attention to it.

Got on the highway, rolled down the window and heard it was again. AC and climate control was all off so not that.
it's a very consistent rhythm, 2-3 seconds whirring 2-3 seconds silence etc and doesn't change with acceleration, coasting or when in park.
Sounds like it's coming from drivers side, but I haven't popped the hood to really check it out yet. And really wouldn't know what to be looking for anyway.
My cheapo obd scanner shows no error codes

2012 base model 6cyl stx

Any ideas?

 

The only thing I can think of that cycles on and off independently of engine RPM and vehicle speed is the cooling fans. Pop the hood and see if that's turning itself on and off.

 

That sounds reasonable..
Still haven't popped the hood, I work 14-18 hr days this week.
But I did get a chance to listen to it for a minute. Kinda sounds like damaged bearings/bushings on an electric motor when it whirls up..

 

Well.. think I found the problem
Believe what I'm looking at is the pulley for the water pump.. it's bouncing around like a teen girl at a taylor swift concert

 

If it’s an EcoBoost check the electric vacuum pump. It could behave like that.

 

Finally had a chance to pop the hood on xmas.. Water pump is bouncing around like a rabbit on speed
Guess its time for a trip to the parts store