Hello all, im new to the forum.and unfortunatly my Nitro is actin funny.Ive never had any issues with it,kept all fluids n filters good.@ days ago it over heated,but only to the point that the ding for the light then down pretty rapidy.We had the ac on full that day cause it was cookin out.The ac even went hot so i went to get a refill kit for it.I soon found out its not empty.
So I checked the coolant and its full.Now the truck gets to just about at the "H" mark and goes down rapidly.So no leaks, Fliuds full, waterpump is good also, thermostat is good,No coolant in oil,seems to overheat when ac is on or not. Im lost. Was thinking maybe heater core, A/C fan?

 

2 issues, depending on the mileage, truck may need a good back flushing and system check, the clutch to the cooling fan maybe on its way out, also depending on mileage, the serpentine belt could be slipping and should be changed

 

I also have a 2011 Nitro, my overheating was due to a small leak into cylinder #2 through the head gasket. If the coolant system cannot hold pressure the boiling point lowers and will overheat your engine. Also if you have air pockets in the cooling system that can also cause issues. If you were ever low on coolant you need to get the air out of the system. Also like superdak05 suggested a cooling system flush may help as well.