re-read this thread and saw a piece of plastic inside the rad hose where the neck snapped off the old rad. I see you figured out how those clips that hold it in work. Is it possible a bit of plastic got sucked into the water pump? This is highly unusual (a jammed impeller)

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body. '87 300D w/ Sportline suspension. No more '79 300TD w/ 617.952 engine at 367,750, it was my annual driver to Texas and I sure don't miss it poor A/C heater system!