it could possibly have either a blown head gasket or intake manifold gaskets leaking
thermostat is more than likely stuck shut from the overheat. Have to be changed.
I have a promblem with that too, my car would overheat very fast, it was a faulty NEW thermostat. It still runs hot, I think I need a new water pump
Stuck thermostat, clogged radiator.
if it is a v6 it would be the notorious plastic impeller water pump...they crack off the shaft internally... Scuba
water pump may not be worn out, heater core may be clogging
first of all, do you have the right thermostat? ie: winter, summer. if so i would get the radiator checked, it may be getting pluged.
Assuming it did not overheat before you replaced thermostat and water pump you may have installed the thermostat backwards. It is also possible the cooling system wasn't refilled properly and was air bound.
A stuck or incorrectly installed thermostat.
Usually the car would run cool, unless the thermostat is stuck partially open.
If you drive the Dart like I would (like a bat out of hell) the car would most likely overheat from fast acceleration, and more strain on the engine than what is needed. If you drive legaly, it could very well be the thermostat. Be sure that you use the correctly dilluted antifreeze.
The radiator fan is not working,or not working properly,or possibly the thermostat is bad.But,usually if the thermostat is bad the engine would still overheat even if you speed up,so I would suggest testing the radiator cooling fans.
the first thing i would look at is the thermostat if its not opening and closing at the right time this will cause your enginr to overheat.