Note that the tensioner resides close to the coolant pump. A worn bushing in the tensioner may make some noise, so don't confuse it with the pump.

Based on my experience and from what I've read in this forum, you can get about 100-120K mi. out or a typical OEM pump before it gives out completely...

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car