I would also check the distance from the fan to the radiator. A good rule of thumb would be 3/4” to 1 1/2” away from the radiator. Any more distance and a shroud will be beneficial. Have you ever replaced the t stat with a new one?
Never replaced the thermostat, I was told its unnecessary since i dont have a working heater in the car, figured id install it when i install the heater stuff
