VAPOR LOCK

Another piece of info that may or may not apply to your particular vehicle. Cooling systems with the overflow tank are designed to run with zero air in the system. Some vehicles are very sensitive to this and will overheat if air is present. Some have bleeder valves to bleed the air out, but in any case air can usually be removed by turning on the heater temp to full, removing the radiator cap (on a cold engine), topping off with coolant and then running the engine at a fast idle with the radiator cap removed until engine reaches normal operating temperature. During the process keep a watch on the coolant level and keep adding more as the air bubbles out. At some point usually within ten minutes or so the bubbles will cease and you will only see coolant swirling around. Top off again and replace cap, then make sure coolant level in the overflow tank is within range and the overflow tube is connected and in good condition.