How to Clean a Car Cooling System

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Corrosion and oxidation products from your engine block, radiator piping and hoses can accumulate in the coolant, leading to build-up and clogging of cooling system pathways. You can clean and flush your car’s cooling system with a product designed to remove corrosion residues and keep the system working properly.

Skill level:

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Things you need

  • Cooling system flush/cleaner product
  • 6 to 9 quarts antifreeze coolant
  • Locking pliers
  • Large pan, metal or plastic
  • 5-gallon bucket
  • Water hose or bucket

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  1. 1

    Check to see that transmission is in "Park" and emergency brake is on. Make sure the engine is cool, then loosen the radiator cap. Place a large pan under the radiator drain, and turn the cock or plug counterclockwise with pliers to loosen it and drain the coolant.

  2. 2

    Empty coolant from pan into the 5-gallon bucket, and place the pan under the engine block drain plug. Unscrew drain plug counterclockwise and drain coolant from engine block. Replace and tighten engine drain plug, and tighten radiator drain cock.

  3. 3

    Pour cooling system flush/cleaner product into radiator. Fill the radiator with water and replace and tighten radiator cap

  4. 4

    Start engine and turn the heat selector to high setting to allow flush solution to circulate through engine block. Run engine for 5 to 10 minutes, or as indicated in flush product instructions.

  5. 5

    Let engine cool, then drain and dispose of flushing fluid, following the procedure in steps 1 and 2. Refill the radiator and engine block with clean or filtered water and run the engine again for 5 to 10 minutes with the heater setting on high.

  6. 6

    Let the engine cool again and drain as before. Now refill the cooling system with about 50% antifreeze coolant and 50% water. Run the engine for about five minutes and check coolant level in overflow tank. Top off overflow tank to warm engine level as needed.

Tips and warnings

  • Some cooling systems have a capacity of 14 to 18 quarts (4 ½ gallons), so you will need one or two large pans and a 5-gallon bucket to collect all the coolant. You can also buy a specially designed collection pan for radiator flushing.
  • If your radiator doesn’t have a drain cock, you will have to remove the lower radiator hose by loosening the hose clamp and pulling the hose free.
  • Dispose used coolant at a municipal collection point, commercial garage, or if regulations allow, dispose in a household drain or toilet.

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