The heater core sounds like it may need to be replaced or the system needs to be flushed again. You said the coolant was full correct?
2008 JK Rubicon
-255/80/17 BFG KM2s, 16/59 JKU springs, 2013 Rubi rims, RC stubby hybrid front bumper, XRC8 winch with synthetic line, RR evap skid, and more to come
1959 Willys Wagon
-Going to be restored and painted Plantation White and Presidential Red
"I would rather wake up in the middle of nowhere than in any city on earth."