Nov 6, 2011

Hairline Crack in Plastic Radiator - How to Repair It

A radiator is a vital part of every engine that runs on fossil fuel because it prevents the engine from overheating. Water is used as a cooling fluid in radiators which is why most vehicle manufacturers use plastic to make radiators and prevent corrosion. Water inside the radiator absorbs heat and carries the heat through the radiator's cooling fins where it is dissipated by air passing through the fins. Radiators are durable devices, but hairline cracks can form on its plastic due to the high pressure inside. Know how you can repair hairline cracks and avoid an expensive radiator repair.

Materials Needed: 

Cold-weld patching compound
Drain pan
Disposal container 
Shop rag
Blow dryer
Utility knife
Plastic knife

Step 1

Locate the radiator leak and mark its location with a marker.Go to your local auto parts store and buy a tube of cold-weld compound that is used by mechanics to repair radiators. Ask the clerk to recommend a product that can withstand engine temperatures of up to 500 degrees Fahrenheit, have the strength of steel, and possess the ability to be impervious to water, gasoline, chemicals and acids.

Step 2

Locate the leak and mark the spot with a pencil, then turn off the engine and let the engine cool. Remove the radiator cap and locate the drain plug under the radiator. Sit a container below the plug and unscrew the plug counterclockwise with a wrench to allow the water to completely drain into the container. Wipe the leak down with a shop rag and acetone, then dry the area completely using a blow dryer. Push down on the crack lightly to get in between the edges of the cracked plastic and dry.

Step 3

Rough the area around 1 inch from the crack using very rough sandpaper, then score the area around the crack using the sharp edge of a utility knife to make a few deep scratches in the plastic. Take care not to puncture the plastic or make the crack bigger. Apply enough pressure to make some gouges on the plastic. Clean the area again with acetone, then blow dry the area to remove moisture along the cracks.

Step 4

Read the manufacturer's instructions on how to use the cold-weld compound. Apply an equal amount of chemical from each tube of the compound on a piece of cardboard, then mix both materials together thoroughly.

Step 5

Apply the mixture with plastic knife and cover the entire crack up to an area approximately an 1 inch around the crack. Squeeze some compound into space along the crack and build up the compound to about 1/8 inch thick. Blow dry the compound about two minutes to help it harden. Neatly wipe off any excess mixture using a shop rag.

Step 6

Allow the mixture to cure overnight. Replace the radiator plug and fill the radiator with a mixture of 50 percent water and 50 percent radiator fluid. Replace the radiator cap, then run the engine on idle for 40 minutes. Watch for any leaks in the patch area, but expect some steam from residual water.

Resources (Further Reading)

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