Diesel that sounds like a tank!!

[StevesPimpWagon]

Hi, my c class 1999 V5 250 tdi, currently sounds like a tank "knocking" under 1500rpm. But is fine above 1500rpm. What could this be ?? any advice greatly appreciated.

 

[colechelle]

Poss a derv knock, could be over fuelling on the injectors???

 

[rpe2]

Hi, my c class 1999 V5 250 tdi, currently sounds like a tank "knocking" under 1500rpm. But is fine above 1500rpm. What could this be ?? any advice greatly appreciated.

Poly belt tensioner?

Richard

 

[Deutcha]

I would also be interested to hear the likely cause and solution of this problem. Good luck.