The check valve we spoke of is located in the oil filter canister. Once it is replaced with the chain tensioner and new rails, the noise should be gone. I have done a few of these with good results.

I would take of the valve cover on the right side and BE SURE that none of the rails are broken. I have seen them break only on the bottom and it is hard to detect.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS