Your father is right. However;
You can effect a permanent repair with epoxy resin. Better to use Devcon which has a higher temp spec, but garden variety araldite will work just fine.
I never really respected my father’s job as a dentist until he showed me how to plug a leak using dental tool to cut the hole enough to work some epoxy in so that it mushrooms on both sides thus can’t fall out. Has to dry for at least a full day. Make sure to use a solvent to clean the area first.
Best if you can rubber bung both ends & have a tire valve in one end, chuck the set up in a bucket & pump it up a bit looking for leaks.
If you have a tear you will have to get it welded but find a person who likes welding thin ally.
PS beware of rad leak ‘fix in a can’ solutions that will reduce the efficiency of your cooling.