Does anyone know what this noise could be?

[78F350]

Originally Posted by blue62

... you could remove the engine cover behind the seats and have a listen.
Use a piece of hose (like garden hose or heater hose) like a stethoscope.
That way you can pin the noise down better then just listening in the normal way.

You could remove the fanbelt and run the engine for just a few minutes to see if the noise stops.
if it does then the fan belt tensioner or the altenator or the water pump is the issue.
...

I can't get the video to play, but I agree This is the best advice so far.

No harm in replacing the AOS preemptively whether it was the problem or not

Since the video didn't work for me, extra questions:

• Is it only driving the car or just engine running?
• Noises up front could easily be a bearing on an idler pulley or belt driven accessory.
• Two fans on the right side - engine compartment cooling and SAI Blower.
• Loose spark plugs chirp.
• Wheel bearings or brake related noises when the car is moving? I had an E-Brake pad drag that made a whine.
• I'd expect that vacuum leak large enough to make much noise should be large enough to trigger a check engine light.
• Exhaust leak at the header/O2 sensor?