W220 Knocking behind dashboard when going left

[design guru]

I have a w220 S320cdi, just recently I noticed a knocking sound almost like several golf balls rolling around in a over size tube hitting each other on the passenger side behind the dashboard when bearing left over 30mph.

Its nothing in the glovebox, sound like something has come loose but strangely it will not make the sound when bearing right, its only on left bends.

Any suggestions? I guess its difficult to guess without hearing it so I will try to upload a sound file.

 

[design guru]

Well I found the problem, the 3 way heater hose was cracked, not sure how it was making noise but the hose from the windscreen washer had snapped off clean. I was losing water but could not find the source, I thought it was from the water pump or alternator cooling pipe.

Replaced the pipe which only cost £7 from Mercedes and the knocking has stopped. Had to remove the rain cowl from passenger side to access the pipes behind the firewall.

 

[Sprint-Man]

Brilliance will always show through, glad you found the problem and made a repair!
Might help someone else too?