And not sure, but I wonder if the hole you have circled in blue is an access point for inserting a pin to keep the tensioner arm de-tensioned when putting on the belt? Then once the belt is in place, the pin is removed and the tension arm is then allowed to put tension on the belt?


Again, no experience with this setup but the above is my best guess.

__________________
Stephen
2010 e70 35d- now driven by son #2
2005 e53 3.0 - now driven by son #1
2021 G05 45e PHEV - now driven by me
2008 ML320 CDI - driven by wife