After reading thses posts, I had mine checked out prior to making the long jaunt for the holiday weekend.

Turned out it was cracked. MB did cover the cost of the part and I was just responsible for the labor.

Noticed that the engine was noticeably quieter at idle since the swap...

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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