Overheating, temperature gauge was climbing to well above halfway?

I recently replaced pretty much my entire cooling system on my vehicle listed above about 2 months ago. Now in the last 2 days I noticed when I was driving with my cold air on, not my A/C, just cold air, the temperature gauge was climbing to well above halfway. I never noticed this happen before. It's also the first time I drove with the cold air blowing for 20 to 30 minutes. I tried to bleed the air out, but I was not sure if that was the problem in the first place. The upper radiator hose is very hot but the bottom one never warms up at all. I have plenty of heat in the cabin. I'm not sure what is wrong especially since I just replaced the radiator, water pump, thermostat, hoses and the belt. It takes a while of driving before the temperature gauge goes above halfway. Generally, about 20 to 30 minutes. That's with the cold air blowing. When I notice it getting high, I crank the heat on, and the temperature starts dropping.