Water Pump Bad? Something else?

1985 Carbureted GT Mustang. Replaced the Radiator with a Hi Performance one. I had to remove pulley fan (not electric) which attaches to the water pump housing (I believe). When I run the vehicle now, the temp goes way up, and hoses and radiator are not hot. I shut down vehicle and haven't run again for fear of damage.

Am I correct to believe that the water pump is the most likely culprit. It is probably the original (108,000 miles). Did I do something wrong when reattaching the fan to the pump assembly? (Maybe over torqued?) or is this a coincidence?

Thanks

You put the fan back on right? How about the fan shroud? How close to the radiator is the fan? Does it overheat at idle, in traffic, driving down the interstate, or what? Did you take the serp. belt off? If so you re-routed it the same way it came off correct?

Yes, the shroud is back on right, as well as the fan. The belt did not have to come off.

I drove the vehicle around the neighborhood at 30 mph. If the coolant is hot at the sensor, then it should be hot everywhere else in the system, right? Unless the pump is not performing, or the thermostat is stuck shut?

Thanks for the reply.

Are you sure you got all the air out of the cooling system? Boil the thermostat to rule that out. Then go back and make sure you dont have an air pocket stuck somewhere in your cooling system.

I will bet that you are correct. Thanks for the insight!