Sounds like your radiator is stopped up & not letting the coolant flow like it should ,, just experienced this with my own truck and now i have to replace head gaskets
!! Mine had started running hot this year and i figured it was just the clutch fan going bad because everything pertaining to the cooling system was still new and checking out as "ok" and my temp gauge never showed anything over 210 at the hottest ,,, i never really got alot of heat from my heater either , even when the truck was running hot and it has a new heater core in it ! one day in town traffic it all the sudden started shakeing and idleing rough for no reason and i could smell a hint of antifreeze every so often while driveing , got it home hooked up the scan tool and no codes , but the temp was at 221 on the screen and my gauge showed just under 210 ! i raised the rpm`s up by holding the throttle open and thats when i saw ( after it was too late
) the problem , when i raised the rpm`s the hoses swelled up at the connections/clamp area and the heater hose that runs along the back of the engine area was kinda pulsating ? and then they would go back to normal for a few seconds and then start the process over again ,, i let it go back to idle and pulled the cap off and looked into the radiator and i seen what was happening , the pump would suck the radiator dry on the outlet side and build up pressure and then force the fluid through the the engine and back into the intake side of the radiator where the outlet side would fill up again and start the process over !!!!!!!!!! I went and bought a new radiator from A/Z and put it in and now everything works like it`s supposed to , no pressure build up or surging in the hoses , nice even flow when the t-stat opens and the temp on the scan tool never goes over 200 even with all the accessories on and a/c idling in the driveway , and ,,,,,,,,, i have excellant hot heat ( not luke warm like before ) blowing out from the heater now !!! but i still have to replace the head gaskets though , the pass side is leaking to the outside of the engine ,, which is better than to the inside !!