How to Fix a Hole in a Radiator

Written by lisa musser
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How to Fix a Hole in a Radiator
You can save money by repairing a hole in a radiator yourself. (radiator humour image by John Sfondilias from

Car parts such as radiators wear out from age and use. Over time, cracks can form in a radiator, causing the radiator to leak fluid. A radiator leak will leave a messy puddle in your driveway and affect the performance of your car. It is relatively easy to repair a small radiator hole or crack yourself. First, visit an auto parts store and purchase a tube of J-B Weld, Quick Steel epoxy putty or other sealing compound that hardens when dry.

Skill level:
Moderately Easy

Things you need

  • Dry rag
  • Epoxy sealant
  • Sand paper

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  1. 1

    Check the radiator for leaks. Examine the radiator closely and make sure the leaking fluid comes from the radiator and not one of the hoses.

  2. 2

    Locate the hole. If the hole or crack is not clearly visible, fill the radiator with water and check for drips. Once you have located the hole, drain the radiator and dry the area where you found the hole.

  3. 3

    Roughen the area of the hole with sandpaper. This will allow the compound to attach to the radiator. The sealant will harden over the crack and fill the hole.

  4. 4

    Mix the compound with a plastic knife, tongue depressor or other suitable object. If using Quick Steel, mould the compound with your fingers to the right consistency.

  5. 5

    Apply the compound to the hole or crack. To harden, the compound will need to sit undisturbed for a minimum of four hours.

  6. 6

    Refill the radiator with water and check for drips. If no drips are present, drain the radiator and refill with a mixture of water and coolant.

Tips and warnings

  • Alternate methods for repairing a hole in a radiator include pouring a product such as Stop Leak in the radiator when the radiator is hot to seal the leak from the inside. Cracking a raw egg into the radiator or adding a small amount of black pepper can also sometimes work. However, using stop leak or the raw egg method may leave particles floating inside the radiator.

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