You should flush out your cooling system on a regular basis; but not everyone does this. Ignoring this maintenance could lead to problems with leaky gaskets, overheating and rust in your radiator. To clean rust in your engine radiator, flush the cooling system using the following steps.
Make sure your vehicle is cold. Do not begin work on the radiator until the vehicle has stopped running for at least an hour and is completely cool.
Turn the radiator cap counterclockwise with your hand to remove it.
Place the drain bucket underneath your radiator. Open the draincock at the bottom of the radiator, using your hands, and let the contents drain into the bucket below.
Close the draincock and pour the coolant flush product into the top of the radiator. Top off the radiator with water from the water hose. If your cooling system is more than 12 quarts, you may have to use two bottles of coolant flush. Reinstall the radiator cap and turn it clockwise to tighten.
Start the car and run the engine for 10 minutes with the interior heater on full blast. This will bring up the temperature of the engine and open the thermostat, allowing the flush to circulate through the system.
Turn off the engine, and let it sit for an hour---or until the engine has completely cooled.
Repeat Steps 2 through 6.
Remove the radiator cap after the engine has cooled again, and fill up the radiator with approximately 50 percent coolant and 50 percent distilled water.
Close the radiator cap and run the engine for 20 minutes so that the water and coolant can mix together.
