How to Clean an Auto Radiator
- 1). Drain the engine coolant from the vehicle. Place a clean container under the drain plug for the radiator and remove the plug. Once the coolant is drained from the radiator, move to the coolant drain plug for the engine block and remove the remaining coolant from that end.
- 2). Pour the radiator flush solution into the radiator. With the drain plugs reattached underneath the vehicle, open the radiator cap on top to pour the solution. Fill the radiator the rest of the way with water after pouring in all the solution and replace the cap.
- 3). Start the car engine, wait for it to reach its normal operating temperature and turn the heater on to the maximum. Let the car and heater run for 10 minutes.
- 4). Wait for the engine to cool down (the radiator cap must be cool to the touch) and drain the cleaning solution using the same procedure as with the coolant. You might need another drain pan or container if the one with the old coolant doesn't have enough room.
- 5). Refill the radiator with fresh coolant. If you are not using a premixed coolant, fill the radiator with a mixture of half coolant and half water.
Source...