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When the car is overheat try to ad new coolant it might be that you have not gotten all the air out of the engine. That is the only thing I can think of when I am reading your description. If you are very sure of the fact that you have all the air out of the system you can have it tested for exhaust gas in the coolant at a radiator repair service station. That should give you the best idea as to what to do.
Please if you need more assistance ask before just rating me as I cannot see your car and are only making assumptions from what you tell me.
I always do the following. Fill the reservoir with coolant until full then with the cap removed, I start the engine let it idle, I then use my hand to squeeze both the radiator hoses in turn to push out the air. The coolant will also come out until the air is mostly out. Let the engine idle until the fan kicks in at around 95 or just over the half way mark on the temp gauge. The termostat should also be open now and both the hoses should be hot. The coolant should also flow in the reservoir. At this point it might suck all the coolant from the reservoir so just ad until full. Then you can close the reservoir and see the the coolant are stable. If it is, switch the engine off let it cool down and see that the coolant level is correct.
People might have other ways that they do it but this is how I do it and it work very well. There are no air bleeders on this car.