Noise on clk270

[Leighton 270]

Hi all some advise please. I have a 03 clk270 cdi auto. It has developed diesel\piston knock sound at around 2-2500 rpm on light throttle. As the auto box changes up you can hear it,or if you put it in gear manually and raise the rev's , but only on light throttle or cruising. If you accelerate hard there is no noise at all. There is never any smoke or does it loose any power. The problem is a lot worse when cold can anyone help please?

 

[tec]

The 270 engine is not exactly quiet.

Can you record the noise and upload it so we can hear it?