Hello, I have a 2007 BMW 118D N47D20A 232k KM and I noticed a strange noise when slowly accelerating between 2000-3000 RPM. This doesn't occurs always and the sound is slightly lower when the car is heated up (after 10-15 minutes of driving).
The car accelerates normally, starts immediately and the service interval was done always under 10k KM using only good oil.
I went to a mechanic for a check-up and we are sure that the cause is not one of the following:
- the timing chain (was changed at around 200k)
- engine mounts
- accessory belt, rollers, crank shaft pulley and engine cover rubbers were changed with OEM parts
Does anyone have any idea what I should look for? The noise is annoying and I want to make sure the engine is fine.
Thank you in advance!

Here are two videos of how the noise sounds (videos are not mine):
https://www.youtube.com/watch?v=jKX_...hannel=ToniTon
https://www.youtube.com/watch?v=cTp5...hannel=ToniTon