Well, I appreciate the responses. Like you said, it looks like we are both partially correct. So, in my 83 300D, will hot coolant flow through the heater hoses but not the heater core itself if the heater itself is not turned on? I'm wondering, as I know several people that use WVO use a flat plate heat exchanger and plumb it into the heater hoses. Are they not getting hot coolant through the heat exchanger if the heater is off??

thanks,

Glenn

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)