Loss of Coolant and overheating

Apparently you still have a leak. I would find another mechanic. It could be a heater hose that is cracked or split leaking onto the exhaust, water pump, one of the main hoses, thermostat housing gasket, etc.

EGR is notorious for stealing coolant. Makes it disappear without a trace. Does the same thing in semi trucks.

The sloshing around under the dash is air and coolant going through the heater core. You need to get the air out of the cooling system. Then you need to have the cooling system pressure tested for leaks. Have any leaks you find repaired. Since it overheats at idle but not while driving you have an airflow problem. Most likely the radiator cooling fans are not coming on. The front of the radiator could also be blocked with dirt, leaves, or other debris. Hope that helps!

Update: I got the air out of the cooling system and the took it for a drive for the first time in over a year the heat started to actually work and stayed working. I then parked it and let it idle. The heat almost immediately stopped working and within 10 mins the temperature almost hit the red. Is it possible that the heater core needs to be flushed as well?

If coolant is still leaking, the engine will overheat due to not having enough coolant in the system. Did you find the leak yet? Also check your fans to make sure they are working.

Thanks for the update! Since the heater stopped working at idle and the engine started overheating the water pump is now suspect. Are the radiator cooling fans coming on? Hope that helps! Jim

Js08016, the fans do come on when idling and overheating but does not help cool the engine down. I will look into the water pump thank you.

Ok, good about the radiator cooling fans! I think the next thing to check is the water pump. Jim