I have a stubborn oil leak behind/beneath the SLS pump in my W124 wagon. The leak is engine oil, not SLS hydraulic fluid.



The SLS pump is mounted to an aluminum plate, and the plate is mounted to the cylinder head. The aluminum plate seals to the cylinder head with a large thick o-ring. Based on where the oil is dripping from, it appears to be leaking from this o-ring.



However, I replaced the o-ring today (along with every other seal inside the SLS pump) and the leak remains . It's a significant enough leak that I can't just ignore it.

The o-ring sits in a groove so it'd be hard to install it improperly. I pulled it and checked again to be sure it wasn't seated incorrectly or something, but it looks fine.

Has anyone had this happen before? I'm not sure what to do about it... A couple of extra pictures and diagrams are attached in case it helps.

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1989 250TD Wagon 5-speed, 160,000mi ::: Dark gray metallic / black cloth
1984 190D-2.2 5-speed, 287,000mi ::: Silver-blue metallic / black MB-tex ::: SOLD