2004 Chevy Impala kept getting hot, Weve changed the thermostat and changed the oil like we were supposed to. It over heated a few more times when're tempature gauge hit 260 I shut it off but after the3rd time overheating it started making this terrible sound sort of like rods knocking but I know it wasn't could someone help me out on what might the issue be?

 

Thermostat opens, water pump pushes the coolant through the radiator, it dissipates the heat and returns to the block and cools it back down. A very simple system when it is working.

When was the last time the cooling system was flushed? (miles & years ago)
What does the coolant look like and is it at the proper level?
Very important --> Does your fan turn on?

 

if you've let it get to 260 you may have caused some serious damage, I'd be getting a combustion gas tester and make sure the heads and/or head gaskets aren't toast.