NO HEAT AT IDLE HEAT ONLY WHEN DRIVING REPLACED THERMOSTAT

Make sure the coolant fan is coming on and the engine coolant temperature sensor is functioning properly .

Your heater core is partially blocked. I know you flushed it, but you can't get all of the sediment out and make it flow under low RPM because of the blockage caused by scale and oxidation caused by minerals in water/coolant. Try to flush it again using CLR, and if that doesn't work, you'll most likely have to replace it. Hope this helped!

is there a chance that one of your heater hoses are clogged? or where they connect to the engine are clogged still? sounds like a clogged system. Cracked heater housing? Outside air bypassing the heater coil while driving?

Usually the problem with no heat and overheating is low coolant, thermostat, or a faulty water pump impeller.
The radiator may not be full of liquid coolant, or the pump may not be moving the coolant thru the block.

Did you bled the air out of the cooling system? Do that and I bet it cures the complaint.

I've notice you skip thermostat.. then the temp sensor.

Have your thermostat replaced it is probably sticking
Make sure your coolant level is full as well.


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Is it overheating to the point of boiling over, or does the guage or light just come on? What i am suggesting is that maybe it's the heat sending unit, or temp. sensor that is faulty. If the thermostat is working, the water pump is working, the coolant isn't low, the fan cuts in and out, and the rad isn't plugged, i would almost say it has to be the sensor. Let me know.

sounds like you have a plugged heater core try taking the hoses off and blowing air through it.

check cooling fan sensor and cooling fan motor