Rattling sound from engine 2015 F15

[ramforinkas]

Hey all,

Started hearing this sound from the engine bay about 1.5 weeks ago. Noise seems to occur only on light acceleration, however often persists after accelerating for several seconds before going away. Any ideas? I posted a short video of the sound below. It sounds like it's coming from the engine or around it. Belt or pulley maybe? It's an 2015 f15 x35i 50500 miles. I've owned it for 2.5 years and no previous problems, maintenance always done on time.

Thanks in advance for any help!!
Sam

In this video I am consistently accelerating lightly.

[RED_Y_]

Sounds like something is loose, some heat shield or something.

[ramforinkas]

In case anyone stumbles upon this in the future, the cause is a failing serpentine belt tensioner. Had replaced for 370.

Thanks!