Check the belt tensioner...mine was swapped out while the car was in the shop for the leaky timing chain cover...engine sounded noisy then, too.

Much quieter now.

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car