A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan. Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes.
To flush a car radiator, ensure the engine is completely cool. You will not be able to work otherwise. The engine is coolest when it has not been operated for at least two hours. This step is vitally important as coolant in a recently-used engine can be extremely hot and can cause injury if it comes in contact with your skin.
1. Place a bucket under the drain valve at the bottom of the radiator.
2. Open the drain valve and allow the liquid to drain into the bucket.
3. Close the drain valve and pour the used liquid into containers with tight-fitting lids.
4. A funnel and some old gallon water jugs do the job as long as you label them prominently and pour carefully to avoid spilling the liquid on the ground.
5. Open the radiator pressure cap and fill the radiator with water.
6. Run the engine with the heater control on High for about ten minutes.
7. Keep an eye on the temperature gauge to make sure that the engine doesn’t overheat. If your vehicle has an engine temperature warning light instead of a gauge, shut off the engine as soon as it lights up.
8. Shut off the engine and allow it to cool down.
9. When the radiator is cool enough to touch, drain the water out of the system into the bucket again, and transfer it from there into a closed container for disposal. Label the containers toxic water to prevent accidents.
10. Close the drain plug and refill the system with water and coolant.
11. Consult your owner’s manual, the back of the coolant jug, or the charts that coolant manufacturers supply to find out the number of quarts that your cooling system holds. Many coolants are now pre-diluted with water, but if you’re buying straight coolant, divide that number by two and buy that amount of coolant. Adding an equal amount of water to straight coolant gives you a 50/50 water/coolant mixture, which is fine for everything but extremely cold weather.
12. The liquid should reach the “MAX” line on the coolant recovery reservoir or cover the fins in the radiator. If it doesn’t, continue to add equal parts water and coolant until it does.
13. Disperse the water and coolant evenly throughout the system.