How to Fix a Hairline Crack in a Cast Iron Radiator


Cast iron radiators can produce reliable heat in buildings for decades at a time but do break down eventually. Since cast iron is such a brittle material, it is prone to cracks. A cracked radiator will begin to leak and allow hot steam or water to escape. This reduces heating efficiency and can pose a physical danger as well. You can repair a cracked, cast iron radiator with an epoxy glue made for use on metal objects.

Things You'll Need

  • Adjustable wrench
  • Large pan
  • Dish washing liquid
  • Wire brush
  • Acetone
  • Work gloves
  • Cold-weld epoxy glue
  • Shut off the radiator's manual control valve. Turn the large knob clockwise until it won't move any further.

  • Close the lock shield valve at the other end of the radiator. Remove the cap and turn the valve with an adjustable wrench until it stops.

  • Remove all rugs and other furnishings from around the radiator. Place a large pan under the radiator drain valve. The drain valve is typically located at one end of the radiator and is mounted horizontally.

  • Open the radiator drain valve with the adjustable wrench. Allow the water to run out of the radiator and into the pan. Close the valve once the radiator is empty.

  • Clean the area around the hairline crack with dish washing liquid mixed with water. Use a wire brush to scrub off the surface paint, primer or rust around the crack. Wipe the bare metal with acetone to remove oil or other residue.

  • Put on work gloves then mix two-part, cold-weld epoxy glue in a one to one ratio. Apply a thin coat of epoxy to the cracked area. Old House Journal recommends that the epoxy be no more than 1/32-inch in thickness. Allow the epoxy to cure for 15 hours or more before re-opening the radiator valves.

Tips & Warnings

  • Remember that the water in the radiator may be hot so take precautions when draining the unit.
  • Always wear gloves when working with epoxy and avoid wiping your eyes as you're working with it.

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  • Photo Credit Hemera Technologies/ Images
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