The radiator cooling fans are not turning on for you. That is the problem. When you sit still, at a red light, there is no air flow through the radiator. Thus, the engine heats up. When you are moving, there is air flow which cools the radiator and engine. When the engine hits a specified temperature, the temperature sensor sends a signal to the computer which in turn sends power to the fan relay which sends power to the cooling fan making it run. The problem could be any of the things I just mentioned including a bad cooling fan motor.
You need to start by checking to see if there is power to the fan motor. If there is, then the motor is bad. If there is not, you need to either scan the computer when it happens to see if the coolant sensor is sending the correct signal to the computer or start tracing wiring back to see where power is lost.
Monday, July 23rd, 2018 AT 11:38 AM