Well if the two are connected, make sure the belt is tight enough with the new pulley. That's the only way it could cause the engine to run hotter.
If that checks out, do the usual things in that situation. Check coolant level, bleed, make sure there are no shopping bags/other debris in front of the radiator/condenser, flush if there are contaminants, make sure cooling fans come on, replace the t-stat if you're still having the issue. If still make sure coolant is flowing properly, check the water pump.
