Had this exact issue. My shop replaced thermostat. Problem persisted and I had to continue to add coolant to reservoir over a 3 day period. But no heat at idle continued.
Brad1 (2CarPros) replied April 6, 2009 to my issue and described in detail how to remove air from cooling system.
I followed the air purge process and problem was resolved. I spent $160 needlessly on stat, labor and coolant. I suspect it was air in system all the time. One symptom was a gurgling or bubbling noise behind glove compartment at start up in addition to no heat idle.
Tuesday, January 15th, 2013 AT 2:28 PM