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Have you started the car with the radiator cap removed?
First of all I want to make sure that you bled all the air out of the coolant sys when you filled it and that the coolant fans cylcle and it does not run hot at idle.Next, if you started the car with the radiator cap removed and it did not push water out of the filler and if you pressure tested the coolant system and did not loose pressure and if when it runs hot it does not loose coolant, the next step is to drive the car untill the car starts to run hot and turn the heater on wide open heat and blower. Observe the temp and if the temp goes down when you turn on the heat, the radiator is not flowing enough and needs to be cleaned/replaced.
Hows the car running?