I have a 2013 C63, having previously owned a 2009 model. Compared to the prefacelift model my facelift model has a few different groans/squeaks and rattles that are more a low level annoyance than a major problem to the extent I have learned to live with them. One noise however had intrigued me, - a sort of metal on metal tap/clunk, barely audible if at all with windows up but definitely there with window down and travelling at lowish speeds over rough roads. I had thought something suspension related, told the dealer who of course said no the suspension checks out fine, we can't hear the noise you are referring to etc etc
Anyway the other day I closed the hood and somehow noticed that when in closed position at the front right corner there was some play in the hood ie you could bounce it up and down slightly and...guess what?? reproduce the sound I had been hearing for the past 2 years.
The cause was quite simple to fix. Near each front corner of the hood there are 2 metal brackets, which each fit into their own catch to lock the hood shut. On each bracket there is a nut that can be tightened/loosened with an open ended spanner to adjust the height of the bracket. In my case the 2 brackets were of an unequal height so the hood was not being held down securely when in the closed position. A couple of turns with the spanner to set to same length and the noise as gone in an instant.

 

Very helpful, awesome!

 

pics?

 

I have the same noise and will use your post as a guide to maybe resolving it. Thanks.

 

neat! I can confirm that the dealership also fixed a loose hood hatch on my FL sedan that was creating some metal and metal clunking sound when going over rough roads / going up driveways!

 

this?

 

Attached is a photo of the bracket on the underside of the hood. I adjusted the nut at the base of the bracket (not the bolts attaching the bracket assembly to the hood). The bit you have marked I did not touch.