How to Clean a Clogged Car Radiator

Written by zyon silket
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How to Clean a Clogged Car Radiator
Flushing a radiator on a regular basis keeps the engine cooling properly. (radiator humour image by John Sfondilias from

Most automotive manufacturers recommend flushing or cleaning out the radiator once per year to ensure the radiator and cooling system remain in proper working order. One of the most destructive things that can happen to an engine is a failed cooling system. If this happens, the engine can overheat, causing thousands of dollars worth of damage. Taking a short amount of time once a year is cheap insurance against coolant system failure.

Skill level:
Moderately Easy

Things you need

  • Drain pan
  • Large container with lid
  • Nozzle and garden hose
  • Water source for garden hose
  • Two gallons of antifreeze
  • Two gallons of distilled water

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  1. 1

    Place the drain pan under the petcock (drain valve) of the radiator and drain the antifreeze into the drain pan. Drain the antifreeze into a large container with a lid. Antifreeze is toxic but smells sweet. Due to this, it attracts children and animals. All antifreeze must be properly stored and disposed of.

  2. 2

    Remove the radiator cap and spray the inside walls of the radiator with a garden hose until the fluid that drains out of the radiator is clear. You need to move the hose in all directions to clear out the antifreeze build up. Routinely check the drain pan and empty as needed.

  3. 3

    Close the petcock and fill the radiator halfway full with antifreeze and then fill the other half with distilled water. Use only the antifreeze specified by your auto manufacturer. Antifreeze is available in multiple colours such as green, pink and yellow. Use the colour that originally came in your vehicle. This will prevent damage to your cooling system.

  4. 4

    Bleed the coolant system. Run the vehicle for 15 minutes in a stationary position with the radiator cap off and the heater on full heat. This circulates the coolant through the engine and forces air through the system and out of the filler cap on the radiator.

Tips and warnings

  • It is a good time to check the radiator hoses for dry rot, cracking or holes while you have the radiator drained. This is also a good time to clean debris off the front of the radiator. To do so, scrub the radiator with soapy water and a soft bristle brush. Gently hose off with the garden hose when finished.
  • Do not drain the antifreeze when the engine is hot. Antifreeze will burn your skin if it comes in contact with it while the engine is hot. The use of gloves is recommended to prevent getting antifreeze on your hands.

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