e320 identify part near tensioner
 

I am replacing the serpentine belt tensioner and when I removed the old one I found a tube about 5 inches long lying loose in the area. I can't figure out where it came from. It is rigid plastic, about 1/4" interior diameter, one side is straight with a ridge about 1/2" from the end , similar to the dip stick tube so that it will rest and not drop all the way in an openning. The other side is curved like a question mark.
the only openning I see in the area is a hole at the top of the water pump but I don't see where it would have connected to. I checked diagrams in the service manual and different part supplier manuals, can't find it.
anybody have an idea what this is?
1995 E320 with M104 engine