09 Prostar running hot

[Rawze]

I have seen people change thermostats and either not change the brass ring in the bottom of the thermostat housing and/or damage it during install. Then, the engine continues to overheat, so i would verify this by disassembling it and inspecting it closely. Make sure the brass ring is undamaged and the turkon seal is not split or broken.

I have seen trucks that the A/C condenser gets dirty and restricks air flow through the CAC and radiator.

I have seen trucks that the inside of the radiator gets anodized, reducing its thermal efficiency making for higher coolant temps as well. You claim you have an after-market radiator, perhaps this may have happened?

I have seen trucks where the engine fan was mounted backwards and it was pushing air forward instead of pulling air towards the engine. Yes this is possible.

I have seen trucks where the fan solenoid went bad and the fan clutch did not fully engage, then it wears out and the fan does not pull the air through well enough after a few months. I have also seen them rust and get dirt in them and cause the same things.

You did not mention the type of coolant you use, or if you have flushed it. Perhaps that is relevant?

A cheap thermal temp gun can work wonders with cooling system problems. You could say .. Check the inlet and outlet temps for the radiator core, check the tharmostat housing to see if your getting false readings, check the temp of the water going into the water-pump, etc.

The water pump is a vane-style pump. If debris went through the pump, the vanes could be damaged, reducing coolant flow, but it is pretty rare for this to happen.