Heat has a way of finding the weak spot in a car. The same vehicle that felt fine in mild weather can start creeping toward the hot side in traffic, especially with the A/C running and the pavement cooking beneath it. That is usually not bad luck. High outside temperatures make every part of the cooling system work harder. If the coolant is low, the fan is weak, the radiator is restricted, or a hose is close to failing, summer driving will usually expose it. Why Heat Finds Cooling System Weak Spots Your engine already creates plenty of heat on its own. The cooling system’s job is to remove that heat, move it through the radiator, and keep the engine within a safe operating range. Hot weather gives the system less room to recover. Traffic makes it worse. At highway speed, air moves through the radiator naturally. At a stoplight or in slow traffic, the cooling fans have to do most of the work. If the fans are weak, the radiator is dirty, or the coolant is not ... read more