If you personally changed it, I would guess theres some air bubbles blocking the hoses.
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.
about 30$ to do it yourself, maybe less.
Was the gasket replaced? Have you checked the hose and the heater core. Is everything tightened down?
The thermostat is stuck open and needs to be replaced.
water pump
Would need to know if car was overheating before waterpump and thermostat was replaced.
not really. the only thing i would change though is the thermostat. Try to get a lower opening temperature thermostat.
Usually this is not the case. It looks like a bad thermostat, because no way the coolant is not getting hot, but a rusted up thermostat would not open for the coolant to circulate. If I were you I will change the thermostat first than check the water pump.
because the water pump is not working properly....
I would have to assume that you need to replace your thermostat. If the temp. gauge isn't getting very hot (around 190 degrees) after the vehicle has been runing for an extended period of time the thermostat is probably stuck open.
Yes it can cause it to overheat but first check your thermostat. That would be the 1st cheapist thing to do before you did anything else. I got an 85 regal(overheating) and the thermostat or the heater core is the problem im getting them both replaced tomorrow and will let know of how it runs.
Year, make and model would help us help you.