My 850 is making this whirring humming noise from the front of the engine.

Some background info:
I took the head off to replace valve stem seals. After putting it back together, I did a full timing belt service with genuine volvo and oem parts. I also replaced front and rear cam seals. I fired it up after making sure timing was good and boom the noise started.

I already ran the engine with the serpentine belt off and verified that the noise is coming from inside the timing cover.
I also ran it without the timing covers and the noise was a bit quieter but it was still there.

Here is a link to a video I recorded of the engine running and making the noise.

some thoughts:
I tightened the cam cover bolts to 15 foot pounds. Could they may be overnightened causing that noise?
my brother thinks we pushed the front cam seals in too far and that is whats causing the noise.
would the belt not tracking totally straight cause the noise?

 

Use your stethoscope to isolate the noise. Just in case somethings wrong with the timing belt installation. $5 at harbor frieght. Cam cover torque is not your problem.

 

Ok so I've recorded some more footage.
And i think i might be onto something now.

Here is a video of my poking at the belt checking for proper tension. I noticed I could move the belt with my fingers witch seemed odd. I also found I could turn the idler pulley with my fingers. But if I turn the engine over clockwise it tightens up. Is this normal? It seemed to have good tension otherwise.

https://youtu.be/9dwgq6ZLm-g
Here is a video of the engine running with the covers off.

https://youtu.be/pyQmINIVtjM​​​​​​​

And here is a video with the engine running (covers off) but strangely the noise seems to have gone away! using a vaccun hose as a stethoscope, i probed that plastic back cover and I think I might have tweeked it or something. Take a listen.
https://youtu.be/5o8I23s-020

 

Did you release the pin in the tensioner when you did the timing belt?

 

yes I did.