I just change my water pump, and before I did I put water in to make find the leak to make sure it was the water pump. After I drained my radiator, put 50/50 in the radiator, and filled it up. I have a 180º thermastat, and it is running around 230º. So I drained it again, and mixed 50/50 with pure antifreeze. I filled it up, started my car, and let it run. It got about 1 line before red then went down about 30 - 40º and started going back up. So idk what to do now, or why it is still overheating?

 

You need to bleed the air out of the system. Air when heated reads hotter then antifreeze. Below is the process pulled from the shop book:
1 - Open the cooling system bleeder screws.
2 - Slowly fill the cooling system with a 50/50 coolant mixture.
3 - Close the cooling system bleeder screws.
3 - Install the coolant pressure cap.
4 - Start the engine.
5 - Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.
6 - Allow the engine to idle for 3 minutes.
7 - Shut the engine OFF.
8 - Allow the engine to cool.
9 - Top off the coolant as necessary.