I have a 2009 2.7L Dodge Avenger SXT

My coolant is bubbling in my overflow tank after I shut the car down. I had the coolant changed at jiffy lube, and it is still happening. I don't overheat, my A/C works but my heat does not. I've bled the line as well as I can to no avail. I'm think possibly a heater core issue or a thermostat issue. Any ideas?

 

Could be a head gasket issue.

 

A few bubbles appearing briefly? Not to worry.

Head gasket, it would bubble while the engine is running. Even a small leak in the head gasket
can allow combustion gasses from the engine cylinders into the coolant system. A steady stream
of bubbles means a break near one of the cylinders, next to the coolant jacket. This is pretty
common for a leaking, or "blown", head gaskets.

If it were a thermostat, it would over-heat.

Clogged heater core, would = no heat.

One problem that would cause "kettling" or boiling is by using too much water in
the mix can lower the boiling point of the coolant mix. Too much water, can cause
the coolant to boil when the car is shut down.

If you don't see it when it's running, then it's not a head gasket.