2001 dodge dakota 4 cyl. overheating

Started with a leak on the upper filler hose. Replaced the upper filler hose, the thermostat and it is still blowing off steam after a few minutes. The thermostat is allowing the hotwater to the radiator. Flushed the heater and the radiator. No other leaks. Tried the new cap and the old one and steam/water still blows off after a few minutes letting it run. The fan does turn on.

I would take the thermostat out and see if that stops the overheating.

Do you get HEAT when you turn the HVAC on Heat high max?

This will tell you, if coolant is flowing through the engine + heater core.
If not, use a garden hose with a little water pressure to force air out of coolant system.

Two questions I would ask.

#1 does your truck have an electric fan?.does it kick in ?

#2 have you checked to see if you have a blown head gasket?

Im thinking you might have a blown head Gasket that releases heat into the coolant system under heat pressure.

This is only a suggestion. I hope I am wrong.