I have a 99 Durango 5.2 Engine it started running hot over the summer when the A/C was on... so I turned it off... still over heated,replaced the thermostat and water pump, flushed system, and replaced fan clutch... ran good till yesterday started over heating again... I am lost replaced everything I can get my hands on and still over heats and ideas... bought a radiaor cap today on the way home heard that could do it but not sure why. Any help would be greatly appreciated..

Eric

When you say you "flushed system," are you sure the radiator is flowing freely through all the tubes?
If any of the tubes in the radiator are clogged, flushing will only clean the ones that are still flowing.
To check the radiator, you need an infrared temperature sensor.
Handheld NonContact Thermometer - MiniTemp MT - Raytek.com
Simply scan the radiator while the engine is up to operating temperature and see if all the tubes are moving heated coolant.
If not, replace the radiator and install a clean 50/50 mix of coolant and water. Purge the air and retest for good flow in the radiator.
I hope this helps.