cold start knocking noise at low RPM

Hi to all,
I have c3 1.4 hdi 2008 and 180 000 km.
During this winter started to make strange noise (knocking) on low rpm wile the engine is cold. Some times the same knocking show up on hot engine. The knocking is not synchronized and and the sound seems to be coming from the belt tensioner. I already removed the tensioner and pulley from it, but I didn't notice any play or damage on it. The knocking continued even after installing the old tensioner back.
This link:
https://youtu.be/A23s1FdEDVQ
is one video what I found on youtube witch have same problem as I have. The sound is happening at 14 sec of the video. Some times is very often, some time is repeating, but does not have any rule.

So, please if someone have any idea what is the problem. I want to be sure before I change tensioner.
Thank you,

Hi

Probably the TVD knocking

see Citroen C3 Diesel Clattering/Rattle



but a 100K, you should change the belt, tensioner, TVD, the water pump pulley and cam belt is probably due. Doing them all together saves time as the parts will need to come off for the timing belt anyway.

Thank you for reply,
I already changed all these parts on 120 000km, with original Citroen parts (timing belt, water pump, both tensioner on the timing belt) but on axillary side I changed only the belt. As I explained in my first post, I checked the tensioner and and pulley and didn't notice any play or damage. So, everything is OK, but I am concerning about that knocking (snap) what is hearing on 14-th second on the video. And that is happening more often on cold engine. 1-2 knocks in 1sec, then 2 sec pause and so on, without any order. I saw the links on the post and I think TVD is not the case.

Any other ideas?
I will try to make record of the sound of the engine and will post it.

Regards,