A vehicle's radiator is a part of the cooling system. Fluid within the radiator acts as a coolant, absorbing heat to keep the engine block from overheating during operation. Cracks in a car's radiator can cause the coolant to leak, resulting in an engine temperature increase that can eventually cause your car to break down. Additionally, small cracks can expand over time and become large enough that the radiator needs to be replaced. Sealing small cracks before they become a huge car problem is the easiest fix and least expensive solution.
Turn off your vehicle if it has been running. Let the engine cool before attempting any repair. Prop the hood open.
Locate the radiator in your engine. If you have trouble finding it, consult the schematic of the engine block in your owner's manual.
Shine your flashlight on the radiator to search for visible cracks. If you don't see any cracks, open the radiator cap and pour in a gallon of water. Bend down next to your vehicle and see if any water leaks out from under your car. The location where the water lands on the asphalt below will indicate a smaller region where you can search for the leak. Shine your flashlight on the radiator again, looking for water leaking out.
Wait until the water has fully leaked out of your radiator reservoir before beginning to seal the leak. Quicken the process by running your car for a few minutes to evaporate the water in the reservoir.
Squeeze the liquid bonding agent onto a piece of cardboard and mix it with the corner of the putty knife. Many chemical bonding fluids will have two separate chemicals that need to be mixed together before their adhesive properties take effect.
Scrape the bonding agent across the crack in the radiator, covering the hole completely. Let it dry for several hours, or as directed on the adhesive package.
Pour another gallon of water into your radiator, and continue to search for leaks. Apply adhesive to any cracks you find to prevent coolant from seeping out of your reservoir.
