WHAT CAN CAUSE A CAR TO OVERHEAT?

You said the water flows thru the radiator as fast as you put it in, did you mean it leaks out? If it is just circulating fast, it could be that the Thermostat is stuck open, which could cause it to run hot. If its stuck closed, it will over heat. It would help if you were clearer with your question. Goodluck

I'm going to give it to you straight when you ran it hot there's a strong chance you may have caused damage to the heads it's a common problem with the northstar engine because both the enging block & heads are aluminum and it don't take much to damage them.

replace over flow bottle wa/pump and the thermostat