my 2000 ranger xlt 3.0l v-6 has started heating up. noticed the temp gauge is climbing to the H instead of staying between c +h. as long as im driving all is fine but stopped at intersection or waiting in line at fast food is when it climbs. flushed cooling system 3 days ago and got clear water coming out and yes i had heater running during flush.still heating up, put in new thermostat and still heating up. burped the system, checked air temp from heater and its luke warm at best. so i know im not circulating coolant through whole system properly.put new temp sending unit in but still the same. so, am i correct in thinking it has to be the pump or the radiator itself being clogged up.any ideas would be great. thank you.