If the repair needs to be done on the tank, not the core, then a good epoxy putty might be a good fix.
Many radiator cores have been repaired with JB Weld and have held up for years. Just be sure to clean the area to be repaired very well. With the price of cores where they are at, it's no surprise that replacing the core is not the first choice for may of us. I'd try a repair first. If it ends up leaking again down the road, at least it probably won't be a full on gash that's leaking- it'll just be a seep from the JB Weld repair. Good luck. Plenty to You Tube videos showing radiator repair with that stuff. My radiator has a JB Weld repair. We'll see how long it lasts...
Last edited by Norcal Dave; 07/23/2017 6:40 PM.