140K on the factory heater core and still going strong...
I do see the occasional heater core flush thread ("no heat on the xxxx side!") but for all the KK's out there I don't think it is a huge percentage. Most of those partially plugged cores don't need replacing, just flushing out. Sorry you were one of the unlucky ones.
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2008 Liberty Sport 4x4 Automatic
Jeepin By Al 4" Lift Kit
BFG KO2’s 245/75R16
Full MOPAR skid plates
Rock Lizard Skink Super Sliders
AtTheHelm Front Recovery System & Roof RackM116A3 Trailer build thread: viewtopic.php?f=72&t=77997