How to Flush Your Vehicle's Cooling System?
If your vehicle's owner's manual has instructions for draining the liquid from the cooling system, follow them. If you don't have a manual, or if it lacks such instructions for flushing the cooling system, follow these steps to flush and change the coolant without endangering the environment.You take off the cap and look at the coolant. It's a nice shade of green, or maybe red, or maybe even orange. It looks good. Should you leave it in? Unless it's colored orange, the answer is no, especially if it's been two years or more since the last time you drained it.
Today's engines are loaded with aluminum components: cylinder heads, water pumps, manifolds, even engine blocks. And the two primary heat exchangers-radiator and heater-are also aluminum. Aluminum needs great corrosion protection to survive, and the corrosion protection in green and red antifreeze is used up in about two years. Orange offers longer life, but if your car came with green or red, you can't switch to orange without a fair amount of preparation. And if your car is much more than four years old, a switch is not likely to yield long-term coolant life-you'd still face the usual 2-year drain interval.
If the system has a heater coolant valve, close it by moving the temperature control lever or knob to cold. With the engine running at fast idle and warmed up, have a helper move the lever or knob to hot while you listen at the coolant valve. If after the first rush of coolant you hear a continuous gurgling noise, there's still air in the coolant, and you should be prepared to watch the coolant level in the reservoir over the next few weeks.