I changed my thermostat and radiator. Still overheating. How could I be sure it’s the water pump. Overheating occurs when vehicle is at a standstill

 

Try "burping" the system.If system is cool to the touch,remove rad cap.Then, veh in park and E brake ingaged start the motor at idle.,coolent in hand start filling the rad,watch the flow,this allows the system to bleed off the air in the rad.If bubbles show keep adding water or? to the system just until the flow is smoothwith NO bubbles.Put rad cap on and you should be good to go.Just a thought.......................................