Why is my 03 Buick century keep over heating?

I have a 03 Buick century that keep over heating it had a brand new thermostat and new water pump and radiator please help I have no clue why it keep over heating

Other answer:

mack Harper:
Others answered bad head gasket, or cracked head, quite possible. However these cars are NOTORIOUS for blowing the intake manifold gasket. Been there, done that, didn't get a tee shirt. You will need a coolant FLUSH, an oil FLUSH, and quite possible a new coolant level sensor (it got contaminated by oil)
Been There, Done That.:
Was the car checked for a bad head gasket? That's a possibility
Stan:
Could be a blown head gasket.
g:
The other likely culprits would be a failed cooling fan, blown head gasket, or cracked engine block.
steve:
HEY !!!! Heres an idea….Lets start out simple….Ok?
Pop the hood….Now turn on your defroster…..Did one of the fans click on ? If not, have someone check the temperature sensor…..
The defroster makes your A/C compressor cycle on….Any time that happens at least one cooling fan will kick on automatically….
The bad news is, all these other answers you got, are complete BULLSHIT from people who have no clue as to WTF they are talking about….They are telling you worst possible scenario
DavidB:
Did the people that installed the new radiator do a complete flush of the cooling system?I suspect that they didn't and your new radiator could be clogged with sediment as a result.