Have you ever popped the hood on an OM603 equipped car and actually looked at the radiator? Or any modern car for that matter? The tanks are plastic, with the core being aluminium.

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Garage:

2017 Chevy Colorado Diesel (nanny state emissions)
2005 Volvo S40 T5 AWD, 77k
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 113k - 28.6 mpg

WARNING: this post may contain dangerous free thinking.

I think the reverse is probably true, that he has never seen a solid aluminum radiator in a Mercedes-Benz. Stock is aluminum clamped hard onto, crimped onto the plastic. Amazing that it holds that well for as long as it does. On my 300SDL it blew out at about 350K. That’s why I couldn’t see any steam leak under the hood when I pulled over. The leak was 6 or 7 inches wide. The coolant was mostly gone, steam was left.

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1986 300SDL, 362K
1984 300D, 138K