Low frequency knocking sound at hot idle only.. DMF?

[T_nship]

Finally got my car back from dealership after getting PCV, Thermostat, Waterpump done. New to this car and just now getting actually put some miles on it. I’m noticing a low frequency knock that appears only after a drive that has fully warmed the engine up and is present only at idle and when shutting the car off as it’s spinning down to 0 rpm. It sounds in my opinion akin to a rod bearing though I’m certain that’s not it. At first I thought possibly it was a sound from the blower but it doesn’t really make sense and sounds to be deeper in the engine compartment. If I even just blip the rpm’s to 900 it goes away. This is a DSG car. High mileage at 146,000.. I’ve done some digging online and came up with the possibility of the Dual Mass Flywheel having excessive play. Does this seem right? I can’t find a lot on the forum about DMF’s and this is my first car that uses one. If anyone knows, what is an easy way to check for this being the source of the sound short of removing the trans? Is this a fairly common failure on these cars as the mileage gets up there?

[T_nship]

I couldn’t find the edit button but when I say akin to rod bearing sound, that’s my closest reference as it actually sounds slightly deeper and lower but not exactly in harmony with engine revolutions as a rod bearing would sound, but a little more out of pace and not as consistent as a rod bearing would sound.

[Torsen]

If it's a single 'clack' or pop just as the engine stops rotating then yes - that is likely the DMF unloading. It can become more pronounced with age but I believe it is relatively normal. If you hear a chatter or 'rock tumbler' type of noise at idle while in neutral, then the DMF may be on its way out.

[T_nship]

A clack would be a good way to describe the sound on shut down, but more like a few “clacks”. Rock tumbler is also a good way to put it, but of course any increase in rpms or load and it’s gone. I will try to upload a clip tomorrow if I can figure out how. My main concern is if there is a surefire way to determine if this is the source of my sound, and if it proves to be so, how much time I may have with it before this would need to be replaced. I have no experience with this type of unit and I’m not at all versed in their service life, or typical failure methods, if it can break completely, or just be noisy, etc. This car is not a daily for me and under my ownership will be lucky to see 3-4K miles/yr but still, I’d like it to be in top mechanical condition so that it could be ready for an impromptu trip up the tail of the dragon at any time :)