2006 K12 1.4 Activ intermittent engine whirring

[zeepeeg]

I have an intermittent whirring from left hand side of engine that presents itself when driving mildly, but goes away when the car is driven slightly harder.
I changed the aux alternator drive belt, but no change.
Sounds like timing chain area, but car throws no codes and runs excellently whether the noise is present or not.
It's only done 53k miles.
I've uploaded the two different states...
Without noise
With noise
Any ideas?

 

[novocaine]

Did you do the tensioner?

 

[zeepeeg]

I removed the tensioner and it was good.
I'm going to run without the belt to see if the noise disappears...

 

[novocaine]

I removed the tensioner and it was good.
I'm going to run without the belt to see if the noise disappears...

Unloaded bearing will sound and spin just fine. Once loaded it can run rough.
1.4 has 2 belts, so you can run without it at least.

Given its intermittent though I'd check your alternator to.

My 1600 is currently doing it on over run, I will be doing the tensioner this weekend, if that doesn't sort it, I'll be doing the alternator. Fix the cheapest first ( i didn't change it when i did the belt) Screw driver stethoscope suggests it's the tensioner though.

 

[zeepeeg]

I'll replace the tensioner next, if it's quiet without the belt.
Thanks for your help