But can you repair them?
Yeah sure, but only sometimes. Proprietary car rad-fix-in-a-can solutions should be avoided as they will ruin the efficiency of the cooling system.
Take the rad off c/w hoses & put a bung in one hose & throw in a bucket of water blow into the other side with a pump clamped into the other hose, or your mouth if you are desperate or a compressor but has to be regulated to a lowish pressure.
This will locate the leaks. It may be possible to get them ally welded by a GOOD welder. Some tradies just love working on thin walled ally, some don’t- pick carefully.
The other option is epoxy. You have to be careful with this but you can effect a permanent repair. The key is clean it up properly. Open the hole enough so that the epoxy can be pushed through & form a 2 sided mushroom so it can’t fall out.
Devcon is great for this but normal Araldite can hack the temperature.
What can happen is the shrouds rub thru the fronts of the rad causing pin prick holes, but usually it’s the result of a fall & it rips the ally.
Good luck & retest your fix. Common sense will tell you if it is irreparable but I’ve seen real twisted ones brought back from the dead with a few fins removed from around the area & a sea of epoxy & it seemed to hold on for good.