How to Clean an Aluminium Radiator

Written by mary lougee
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How to Clean an Aluminium Radiator
Cleaning vehicle radiators keep the cooling system in working order. (Auto image by Ewe Degiampietro from

Aluminium radiators in vehicles occasionally need flushing to clean out the cooling system. Draining the old antifreeze out of a radiator and following it by flushing will carry small debris and any loose metal out of the system from the engine block, hoses and the radiator. Replacing the antifreeze in a clean radiator will optimise its cooling capabilities.

Skill level:
Moderately Easy

Things you need

  • Rubber gloves
  • Bucket
  • Turkey baster
  • Garden hose with nozzle
  • Radiator flush
  • Antifreeze

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  1. 1

    Let the engine cool on the vehicle to avoid burns. Put on rubber gloves and unscrew the aluminium radiator's drain plug on the bottom of the radiator by turning it counterclockwise. Place a bucket under the stream of antifreeze flowing out of the radiator.

  2. 2

    Open the radiator reservoir cap by pulling it straight upwards. Insert a turkey baster and depress the bulb to suck the fluid into the baster. Dispose of all antifreeze in the reservoir by sucking it out and discarding it into a plastic container.

  3. 3

    Close the radiator drain cap and fill the radiator with water from a garden hose with a nozzle. Crank the vehicle and let it idle to dilute any antifreeze in the engine block with water. Let the vehicle run until it reaches its operating temperature and the thermostat opens. Watch the temperature gauge reach the thermostat temperature of 73.8 to 85.1 degrees C and then the temperature gauge will drop slightly to signify that the thermostat opened.

  4. 4

    Turn the engine off and let the vehicle cool. Drain the water out of the system in the same manner as the antifreeze. Close the radiator drain plug.

  5. 5

    Refill the radiator with water and add radiator flush as directed on the package instructions. Start the engine and run it at an idle for 10 minutes or the amount of time indicated on the radiator flush.

  6. 6

    Remove the drain plug while the engine is still running. Pour water from the garden hose into the radiator fill hole in the top of the radiator at the same rate as it flows out the bottom drain plug. A garden hose nozzle will provide variances in the volume of water entering the engine to achieve the same fill and drain rate. Continue until the water draining is clear and clean. Turn the engine off and wait for the water in the cooling system to drain out of the radiator.

  7. 7

    Close the radiator drain cap and fill the radiator with a solution of 50 per cent water and 50 per cent antifreeze. Fill the radiator reservoir with coolant to the full mark. Start the engine and add antifreeze until the level is at the height of the radiator neck. Some of the coolant will enter the engine when the thermostat engages and the level will slowly circulate and lower. Add antifreeze and water until the level does not lower any more.

Tips and warnings

  • Animals are attracted to the smell of antifreeze but it is lethal for them. Soak up any spills of antifreeze on the ground after diluting them with water to protect pets.
  • Opening the radiator fill cap at the top of the radiator will allow the system to drain quickly due to the air pressure at the top of the cooling system.
  • Purchase the 50/50 antifreeze that is half water and half antifreeze so that it is ready for use.
  • Refer to the vehicle's owner's manual for the volume of the radiator so that 1/2 is full of water and 1/2 is full of antifreeze.
  • Antifreeze burns skin and can cause harm to pets and people.
  • Replace antifreeze with the same type that the vehicle requires. Some newer models of trucks and cars use an orange antifreeze while others require the green antifreeze.

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