My car ran fine on a standard rad to be fair. Car was actually running lean, so hotter than normal, and sat in traffic at Ford Fair with a 2.1 ZVH. Might be worth flushing it all through.
Make sure the rad and cooler are right together, I mean sandwiched, touching. Even just a small gap and a good chunk of air will force out taking the easiest route.
What state is the water pump in?