I am not familiar with any significant changes between the 2.5-16 and 2.3-16 engines in this particular area. I believe you should be able to reset the tensioner by disassembling it.

As I understand them, at some point they were changed to be a ratcheting type to avoid chain slap and other potential ills caused running, even if for only a few seconds, without any real tension on the chain while oil pressure builds during start up. If you have such a tensioner, it is feasible that when you took it out it was set to an extension needed to keep the old chain tight. With the new chain, you might have a tighter chain to start with and the tensioner was too far extended to work correctly. I believe it would have to be disassembled and then reassembled to reset the tensioner length to the "starting" position.

Others with more specific knowledge should pipe up. But if the chain fits, the tensioner should also fit. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)