I would recommend replacing the thermostat, and gasket. On the entire football sized housing, there are 3-4 hose connections, and on the inside there are some gaskets as well. You may want inspect all houses and gaskets coming to and inside that housing. I had the same issue myself until it got to the point of overheating and being on the side of the road for awhile. All my coolant had spewed out of the system just about. I replaced the whole housing/assembly. It comes with new gaskets, and new thermostat. Also be very careful of the Sensor on top of the housing. You may as well replace that too. It's $20. I broke the plastic wings off of mine when transferring it to the new part.

 

Thank you. That is what I was thinking I might have to do. I just wasn't sure if that was the issue since it only seems to leak when the engine is cold and the car has been sitting for more than a day.

 

Usually when loosing coolant within or at the thermostat housing it will puddle on top of the transmission. Most common on these are thermostat gasket, and housing gasket, and the T on the radiator cap.
Don’t forget these housings seal as well on the water pump hose, and have a O-ring gasket there too.
Hope this helps!

 

I have also noticed coolant leaking at the T under the radiator cap recently. Is it possible a bad cap is causing all the leaks?

 

Caps are cheap insurance. Buy a quality one such as Stant.

 

The T itself has split. That causes air to come into the system, instead of pulling from reservoir.
Absolutely yea replace that you can get a cheap aluminum one online. Or can get a oem replacement or even a junkyard..
Depends on your budget.
Hope it helps!

 

Well from ur pictures it appears ur engine is slightly different than our 2012 Avenger SXT PLUS with the 3.6L V6....I'm assuming, if it is an Avenger also, that it must be the 2.4L V4 version cuz of how much different it looks from ours. But I know if it's the 3.6L Avenger & ur leak seems to be coming from the air box region then I can almost promise you it's got nothing to do with the thermostat or it's gaskets as u suggested cuz on the 3.6L the thermostat is clear on the other side of the engine/engine bay so it would likely be 1 of the lines that come out & go into the heater core cuz they're fairly close to the air box area & the one line that leads out of the heater core travels right next to the air box before bein routed into the engine oil cooler (or in other words, the oil pump! but Chrysler loves to call it an engine oil cooler due to the fact they run coolant through the oil pump walls in an effort to keep the engine oil cooler by doing so) so u might check that connection & make sure it's not leaking somewhere or maybe the spring loaded hose clamp slipped off (though this is extremely unlikely as those things, or at least all of the 1's on our Avenger, are insanely tight & difficult to even loosen up let alone get completely off of the their coolant hoses) but a large range of circumstances could have happened to cause that specific hose to start leaking so I'd check there & maybe it'd just be a good idea 2do a full system flush & drain & refill with correct type & amount of coolant so you know that's not got anything to do with the leak.... Best of luck.