RADIATORWELD KIT

Cracks of 4 inches or less and holes up to 1/4 inch in diameter. It works on plastic radiator tanks, aluminum and copper-brass radiators, and coolant overflow bottles. It is not recommended for polyethylene or polypropylene parts, and it will not work on an air conditioning condenser, because it is not rated for refrigerant or PAG oil.

J-B Weld rates the kit for permanent or temporary repairs within those size limits, and many repairs on overflow bottles and radiator tanks do last. Whether yours is permanent depends on surface prep, how close the damage is to the size limit, and how much the part flexes and heats. Treat a larger crack on a daily driver as a repair that buys you time until the radiator is replaced.

No. Shut the system down, let it cool, relieve all pressure and make sure the repair area is drained and completely dry. The epoxy will not bond to a wet surface and will not cure against escaping coolant. Wait for the full cure before you refill and pressurize. Set time is 5 minutes and full cure is 4 hours.

Sand the area around the damage with coarse sandpaper and clean it with acetone. Cut the fiberglass patch to size and lay it over the damage before you mix anything. Break the internal barrier in the pouch, mix for about 25 seconds, and apply the epoxy straight onto the patch. You have roughly two minutes of working time, so have everything ready first.

Yes, you can apply another fiberglass patch over an area you already repaired. Scuff the cured epoxy first so the new layer has something to grip, and make sure the area is dry with no pressure on it. If the leak keeps returning, the damage is probably beyond the 4 inch crack and 1/4 inch hole limits and the part needs replacing.

The kit is a two part epoxy resin supplied in a divided mixing pouch, together with fiberglass cloth that backs and reinforces the repair and abrasive for surface prep. The fiberglass is not optional: it is what the epoxy grips and what carries the patch across the damage. Component counts vary by packaging run, so check the pack you receive.