Rattle at idle

[Aluminium]

Hi folks, just looking for some tips on investigating a rattle in the engine bay . . .

The noise is quite loud at idle and more subdued above 1300 RPM, unfortunately I don't have any help to identify if the part shown in the pic rattles a little less as the revs rise.
I'd like to know what this part is, also if indeed it is this part that's making the noise?!

Thanks in advance.

 

[hotstuff]

that's the auxiliary belt tensioner, works automatically against spring tension.
the rattle could be the bonnet catches or most likely the exhaust heat shield between the engine and firewall.
diesels are quite hard to identify rattles with the bonnet off because of the high noise level, but persevere.

Blue skies
tony

 

[Aluminium]

Thanks for the info Tony, so is it normal for the auxiliary belt tensioner to move in that manner (rapid back/forth motion)?

Looks like I need a trip to Stealth to investigate it properly.

 

[Aluminium]

I went to my local VAG specialist (Lion Garage - Leicester) yesterday and they diagnosed a faulty alternator pulley (freewheel), got it booked-in for today and they collected and delivered it.