Homemade auto radiator cleaner

Updated February 21, 2017

Cleaning a radiator inside and out helps car engines run better and last longer. Over time, a car radiator's fluids build up scaly deposits and corrosion that clog the openings and make fluids slow down or stop running through the radiator. Low fluid in a radiator makes the engine run hot and causes damage to the radiator and engine. Insects, dirt and grease build up to clog the air vents in the radiator, causing the engine to run hot. Cleaning the radiator regularly with homemade auto radiator cleaners removes deposits, corrosion, insects, dirt and grease, making a car run better.

Mix 4 tablespoons of automatic dishwashing detergent with 2 cups of hot water in a spray bottle. Stir until the automatic dish-washing liquid detergent dissolves completely.

Remove the positive post clamp from the auto battery. Spray a heavy coating of the cleaning mixture on both sides of the radiator.

Spray the radiator side closest to the engine first with a pressure washer. Spray the water through the radiator air vent with the water spray jetting toward the front of the car until the all the cleaner off of the radiator. Spray the water through the air vent towards the back end of the car for a few minutes. Let the sprayed area dry completely.

Put on safety glasses and gloves. Remove the radiator cap. Put the drain pan under the radiator drain valves. Open the drain valve located on the bottom of the radiator. Larger radiators have 2 drain valves open both. Let all the fluids drain out completely in the pan.

Check with local ordinances about safe disposal of these fluids. Set the fluid aside. Close all the drain valves.

Open the radiator drain valve(s), and let the water drain completely. If the radiator feels hot, wait a little longer before draining the water, so you avoid getting burnt. Close the drain valve(s).

Fill the radiator completely full with 50/50 antifreeze, and add some to the over flow bottle. Let the engine run for 10 minutes. Cut off the car engine, and add more antifreeze if needed. Replace the radiator cap. After driving your car a short distance, check the fluid level in the radiator, and make sure there is enough fluid in the radiator.


Wear a long-sleeved shirt and trousers when spraying down the radiator. The chemical mixture mixed with heavy grime build up irritates skin.

Things You'll Need

  • Automatic dishwasher liquid detergent
  • Spray bottle
  • Adjustable wrench
  • Safety glasses
  • Rubber gloves
  • High-pressure washer
  • 3-gallon plastic pan
  • 1 gallon white vinegar
  • Water hose
  • 50/50 antifreeze (2 gallons)
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