I used to have overheating issues on my 1989 mustang till I replaced the radiator. Before I replaced it I popped open the hood once and noticed that the fan was not running although the engine was at operating temp or even above. It was engaging then disengaging (the fan would ever so slightly move then stop) it’s been a while since I caught that but my mustang still gets hot when it’s at stop lights for an extended period of time. I’m ordering a new water pump and thermostat so I was thinking I should do the fan clutch as well if there is a need.