I recently picked up a 2003 Civic Hybrid as a project that needed a few things done. Since eliminating a nasty tick by adjusting the valves, I've noticed another sound that I can't identify the source of. It's coming from the passenger side of the engine, and not from the valvetrain. It's audible at idle, whether in or out of the car, but can't be heard while actively driving.

Here's a video of the sound.
https://youtube.com/shorts/aJlzx6dbyew?si=3k36mBG9OCG3_lUZ

Any help with this is appreciated, the car will soon be my daily and I need to know if this is something that needs to be addressed right away or not -- or if I'm just clueless, and this is normal.

 

It's piston slap don't worry about it. I've driven 4-5 of these cars and have yet to find one that doesn't do it. For reference, mine has been doing it for 40000 miles with no change to performance and has not worsened.