If your coolant is coming from deep inside the V of the engine, your possible culprits are EGR cooler, oil cooler, or possibly intake seals. All of which can be addressed at the same time, there is little difference in labor between either repair as 95% of the work is the same.

You can get oil cooler seal kits from several vendors that contain all of the gaskets needed to do them all.

All seals are gaskets, rubber seals, O-rings, or metal seals. I have not encountered any RTV anywhere.

If you can work on the OM60x engines, you can handle the OM642. The biggest sore point is the tight packaging. You often have to remove a host of items just to get to what you want to. Like the aforementioned oil cooler seals. It sits in the middle if the V. To get to it you must remove the air intake, turbo, turbo pedestal, intake manifolds etc.

Very doable, but time intensive. There are lots of detailed tutorial on the forum on the how to, and youtube vids should you decide to tackle it. I did mine 2 weeks ago, took 5 solid days, but mine was for an oil leak, so a lot if that time was cleaning. Figure on 3-4 days first time doing it.

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)