A little advise , after you loosen the 19mm on front of tensioner back out the tensioner adj bolt 10 turns . This will make the belt loose enough to remove and re-install going in 10 turns ,then ck for tension you may have to go one or two more in for correct tension but it cuts down on confusion.
Good luck all.
Mercedes Technician 7 Years (retired to Hyundai)
2000 Dodge Durango
98 Mazda truck