What is this round steel thing in my engine?
 

Anyone know what this is, and what it's purpose is? It's loose enough to move and I can rotate it with my hand, so it's not actually securely tightened, but it doesn't come off.

https://ibb.co/K5BDTXp

It is a mass damper , it stops high frequency vibration from the engine breaking the bracket , it should be tight . have you tried tightening the screw?

Hi
Vibration damper?

Iain

Hi Clan, thanks very much. No, I didn't but I will try and tighten it now that I know that it's supposed to be tight.

Cheers

I find I cannot tighten it. The "shaft", for lack of a better term, on which it sits, is securely tightened into the engine bracket, but the circular steel damper itself can rotate freely around the shaft, and doesn't seem to have any sign of visible method of securing it to the shaft.

Perhaps it has been loose and rattling around for so long that the bolt thread has been damaged ?

Anything could be possible, especially with my S80, which I suspect was definitiely built on a Friday after lunch!

I'm working away at the moment, but when I'm back at home with the proper tools, (and the time), I'll investigate it properly.