If your truck is overheating at idle, there could be a few different reasons. One possibility is that the radiator fan is not working properly. Another possibility is that there is a leak in the coolant system. Finally, the thermostat could be stuck in a closed position, preventing coolant from circulating through the engine. If your truck is overheating, it's best to take it to a mechanic and have them diagnose the problem. Otherwise, you could end up causing serious damage to your engine.