Flapping noise on idle ?

[Phuturephantasy]

Recently acquired an S70 T5 to replace the 850 estate that some blind and stupid female genitalia wrote off, car always starts and runs fine, seems to hold boost and have enough of it but have noticed sometimes it makes a quite loud flapping or fluttering sound when idling - any ideas what this is likely to be.

[Harvey]

Could be the DMF worn (dual mass flywheel).
http://www.volvoforums.org.uk/showthread.php?t=145902

[M-R-P]

If you could get video of the engine making the noise, it would make diagnosis a lot easier...

[Phuturephantasy]

Forgot to mention this is an Automatic gearbox , will endeavour to record a video of it tomorrow so you can get some idea of the sound, sounds like a burst balloon being flapped from side to side to me or maybe a playing card in a bicycle wheel lol , not a metallic sound