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I have a dodge charger 2012 and my problem im having is my temperature guage keeps fluctuating… I change the thermostat and that didn’t fix the problem… I have coolant in my radiator reservoir… What else can cause it to do such a thing? Could they be air and needs to be bled and if so how can I take care of that? Please advise thanks

Define what “keeps fluctuating means”? Have you checked for a head gasket failure?

“I have coolant in my radiator reservoir.”

I assume that you are referring to the coolant overflow reservoir.
Even if that reservoir is full, it is possible that the coolant level in the radiator is low.
When the engine is stone-cold, remove the radiator cap, and take a look at the level of coolant in the radiator.
If coolant isn’t right up to the top of the filler neck, then it isn’t as full as it should be.

Cooling system problems can be caused by many different things. First place to start, ask your shop to check for proper coolant fill in the radiator, air in cooling system, cooling system is holding pressure and the correct pressure, and radiator cooling fans are working properly. My guess is the cooling system isn’t holding pressure, possibly b/c of a small leak or a faulty radiator cap.

The main reason for the temperature gauge to go up and down is because the temperature of the coolant goes up and down. When the car is moving, there is air going through the radiator, when you are stopped there isn’t any until the fan comes on. When you go uphill the temperature goes up, downhill makes it go down. At idle the temp will go up until the fan comes on. When the fan goes off the temp will go up. Any wild fluctuations must be described so we can understand more.

It’s normal for vehicle temperatures to fluctuate especially Dodge vehicles. Wild fluctuations aside…I think you are worrying about nothing.

It looks like this car has a pressurized coolant reservoir, and no separate radiator cap.
OP can confirm this (or not).

The cooling system fill location is at the reservoir so one can’t look into the radiator, the cooling system cap is not located there. If this is a 5.7L engine you must remove the engine vent plug near the water outlet while filling the cooling system.

right next to where the thermostat housing is, there is a 1/4" 18 NPT pipe plug in the water pump. It’s an allen wrench, but I forget the size. Remove the plug and then fill the system with coolant mix until it dribbles out of the water pump fill hole. Replace the plug (I put teflon tape on the threads–careful to keep it to the threads and not too long) and keep filling the reservoir.

I warmed the engine to full operating temp and let it cool over night. The next morning I topped off the reservoir and that was that.

It could even be a faulty thermostat, is there a pattern that relates to type of driving?