My radiator is cracked! Is there any way to fix it? Yes!
It is possible to fix a crack in a radiator without buying a new one. You will need the following tools and supplies: a small flashlight, a sharp pick or awl, an alcohol-based solvent, a two-part epoxy putty product that is heat resistant, a razor blade, and some latex gloves.
If your car's radiator is leaking anti-freeze, you may have a fine crack in one of the plastic areas referred to as the "tanks". The first thing you must do is verify the problem. Allow the car to cool, either for several hours or overnight. When the system is safe to open, refill the coolant/anti-freeze to normal level. Start the car and let it warm up, that is until the temperature gauge is about to its half-way mark. Using your flashlight, observe carefully where the leak is coming from. It will be important to determine exactly where the crack begins and where it ends. It’s a good idea to mark the ends of the crack by scratching into the plastic with a scratch-awl or seal-pick type tool. Once the car is cool again, there will no longer be pressure in the system, and the true length of the crack will be less visible.
Now that the crack is identified and marked, turn off the car and allow it to cool completely once again. At this point you will need an alcohol-based product such as carburetor cleaner or contact cleaner to clean the surface of the plastic where the repair will be made. When the area is clean and dry, you must score the surface with a sharp-pointed tool in a cross-hatch manner. Scratch the entire area of the repair; covering the entire length of the crack and beyond by approximately ½ inch all around it.
The surface of the plastic should appear rough with crisscrossed gouges similar to overlapping pound symbols (#) all along the crack. Doing this will properly prepare the epoxy putty to adhere to the radiator and stay in place and leak-free. Now, put on some gloves, and use a razor to portion a 1-2 inch section of the putty material. Take the putty in your fingers and mix the inner and outer parts of it together. It is essential to mix it very thoroughly; continue to knead the putty until it is a uniform color.
Apply the mixture to the prepared surface of the radiator. Work the putty onto the plastic as completely as possible, making sure the edges are smoothed out onto the surrounding area, and there are no edges pulling away at any point along the repair. It will be wise to inspect the work closely to be certain. A crack in a radiator will be inclined to expand under running conditions, and will not forgive any separation of the epoxy from either of the mating edges. If any surrounding parts or components had been removed to create access to the repair area, it will be best not to reassemble them until the epoxy is fully cured. Most products claim to cure completely within 4-6 hours, but it is best not to put heat and pressure to the repair for a full 24 hours.