Answer
Mar 22, 2025 - 02:37 PM
Ah yeah, the oil cooler leak on these is a known issue — especially on the V6 and V8 engines (like the OM642 diesel or M273 V8). The usual problem is the oil cooler seals (gaskets) that sit between the cooler and the valley of the engine. They harden over time and start leaking oil down the back of the block.
Fixing it isn’t super complicated, but it is a bit of a job because the intake manifold, turbo plumbing, fuel lines, and other top-end components all have to come off to access the cooler. Once you get to it, the oil cooler is bolted down in the V of the engine, and the seals are easy to swap out — but definitely use the updated Viton seals (Mercedes revised them to last longer).
While you're in there, it’s smart to clean out the whole valley and check for other leaks like from the turbo oil lines or intake gaskets. And don’t forget to torque everything to spec when reassembling, especially on the intake and cooler bolts.
In any case, getting the manual software would be a great starting point. It's has all the necessary details to help you fix this issue, like the manufacturer's provided troubleshooting charts, torque specifications, and clear step-by-step instructions.
Good luck!
