Getting your radiator fixed by a mechanic can be quite expensive. But if you know how to repair a car radiator, you can save yourself some cash. Note: these instructions are not applicable to aluminum radiators.
Required Tools and Materials
Rubber coated gloves
Trough or test tank
Test plugs open & closed
Use a pressure washer to take out any debris on the radiator. You do not have to use a detergent.
Seal off any radiator openings except for the one you will use to transmit air. Some of these openings are the heater stub, outlet necks and openings due to sensors taken out. Ensure the cap or size plug is a match for the neck size. Do not use an incorrect plug when you repair a car radiator; this could be dangerous.
Locate an opening. Fasten an open stemmed plug that will allow air pressure to build up in the radiator.
Put the radiator in your test tank. Turn the test air on. Set it to no more than 15 psi. Look for any bubbles; this is indicative of a leak.
Get the radiator tube cleaned. You need to do this so the solder will stick onto the core. You can use a sand blaster or wire brush. Remove all the dirt from the tube. If the metal falls off, replace the core.
Set a thin solder coat on the tube. Use the brush to put liquid flux on the tube. Solder and heat it simultaneously. If soldering is smooth and has no gaps, proceed. If not, go back to step 4.
Put more solder along the thinned portions. You don’t have to put a lot of solder. Just apply enough to make the tube height equal to that of the tubes that are not damaged. Put the radiator in the test tank again. Test it.
Tips and Warnings
Blow off the extra water on the area being repaired. If the core is damaged, make sure you handle the radiator carefully. Put on safety glasses and gloves. You may also consider using a respirator. Do not bend over the test plug when examining the radiator. Double check the psi setting so it does not go over 15.
When you are trying to repair a car radiator, make sure you do not inhale the fumes. Consider using an exhaust fan. Clean your hands after cleaning the radiator.