No heat at idle...Heater Core Pump??

All the hoses (including heater core hoses) were replaced. The system was bled though not likely enough because I wasn't getting heat at idle.



I tried bleeding the system and revving a bit with the front of the car on jackstands. This fixed the heating issue for a while but it soon

returned after a couple of weeks



Later I rented a coolant system pressure tester. Unfortunately there wasn't an adapter made for the zionsville expansion tank so I had to use

the universal piece, which isn't completely secure. The needle on the gauge didn't drop for about 40 seconds (just enough time to take a pic

and put my phone down) before the whole adapter piece exploded off the expansion tank, shooting coolant everywhere. With no second set of

hands to hold the tool down while I pumped the system, I decided to just return it. Since the system held the same pressure for almost a min,

it seems that the system is leak free.



Before going ahead an purchasing an airlift, could the issue be of caused by a failing heater core pump?

No heat at idle...Heater Core Pump??