More cooling problems

2000 intrigue 3.5

I have replaced water pump thermostat temp sending unit

I have tried to burp all the air from the system but some times I can drive it all day and the temp never goes above 1\2 way then other days it shoots to hot then back down. dosent matter if its 90 deg or 70deg outside. I also get a popping banging noise down by the gas pedal when the temp gets to the upper temp gauge line then goes away when the temp comes down. Is there a air bleed screw on this coolant system? I know they talk about one on the other motors that came in this car. Would a power flush ensure all the air and gunk is out of the system? My car has 127000 mi on it

Thanks again for all the help
Rob