Having a W124, I'd say they are pretty much on the mark except for the possiblity that the aux circ pump is the culprit rather than the main water pump. The 602 is one of those engines that can hold air forever, so low coolant could easily result in low circulation through the heater core at idle.

About time for a head gasket, too!

I love the guys on Car Talk. Of course, they aren't perfect, get real, they aren't actually looking at the cars! They aren't very knowledgeable about MB diesels, either, but hey, they don't claim to be MB trained techs, either.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!