After talking to a fellow member about this particular job I realized I hadn't followed up on this thread after finishing the project. Plus, the water-cooled oil cooler setup on NA OM606.912 engines in '96 and '97 W210 E300s is unique, apparently, and it might benefit others to have a closer look at it.

Thanks to fellow member Ron Rountree, who also has a '96 E300, for sharing and allowing me to use the images attached to this post (since I failed to take any while I had mine apart). He just recently completed this job on his car.

NOTE: When removing the oil filter housing from the engine be prepared for a decent amount of oil to come out.

Both Ron and I experienced the exact same scenario - failure of coolant passage o-rings. There are four of them, two on each of the pipes that fit between the oil cooler and the engine. The two pipes are still attached to the cooler in the photos, so only the engine end of the pipes are visible. These o-rings are black, and they basically end up rotting and turning to goo. Interesting coincidence that our two cars would have the same failure at about the same time despite the difference in mileage between them.

If you have a '96 or '97 E300 you might take a look in there to check for coolant leaks. I found mine was leaking while replacing the glow plugs. It was not dripping onto the ground. I would not have seen it or even thought to look for it except for having the manifold off for the glow plug job and happening to notice.

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