Following up to close this out. The leak returned (I sort of thought it would). So I bought a new exact replacement BEHR radiator. It's relatively inexpensive, and the original lasted for 105K, so I would consider that a pretty high quality unit.

Easy to install, problem solved 100%, nothing to watch or worry about now.

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D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.