Ford E150 Van Overheating

Hi, guys I have a 1996 E350 Clubwagon with a 7.5L engine that Im having overheating issues. This all started when my water pump started leaking. I replaced the water pump and my overheating problem started. Since then I replaced my thermostat, then my cluth fan then flushed my fluids several times. My truck would stay normal temp when driving straight roads without any elevations. Then when climbing hills the temp will climb up to almost red so Id turn on my heater to help bring the temp down. I would also overheat if I have the A/C on but in slow traffic. My truck does fine as long as its not going up hill or stuck in traffic with the AC on.
So finally I decided to stop by the pick and pull and got me a really nice radiator replacement. Now its running a lot cooler only a quarter on my temp meter compared to half the last time. Now it only overheats with the AC on so I decided to cheat and bought me the biggest aftermarket fan blower that I can fit on the truck. So now i turn the blower on in slow traffic with the AC on. Its a temp fix but I know there is still something wrong with my truck. Does anybody know whats wrong with my truck. I also drove my truck from northern CA to Arizona and was worried that it might overheat on me so I decided to pull my thermostat out for the trip didnt make a difference it still did the same thing. Need help does anybody know whats going on?

G'day, and welcome to AF


If the problem started after you replaced the pump, are you sure you fitted the right pump?

Turn the Heat on high max, are you getting any heat?
Poor circulation of coolant, shortage of coolant, and any air pockets could cause an over heated condition.

1) Use a Prestone flush kit and a garden hose with a little water pressure to force out any air.

2) A plugged Catalytic converter can also cause an Auto to over Heat.
Any local muffler shop can do a back pressure test on your cats.