3 mk2 golfs, 2 mk3 golf. i think, as far as i can remember.
Maybe flushing the coolant system thoroughly first would be advisable then before using a product such as radweld.
I would only use it for very small leaks anyway as i said. That is when it is very hard to see where the leak is coming from, as often the system can leak when under higher pressure ie. when driving.
I would always tell people to sort the leak, if you can see the leak, then fix it, if its only a small pressure leak that can't easily be found then try radweld, but use the precautions that i listed above. That is what radweld is designed for, small pressure leaks, not bigger leaks. Some people probably do keep putting the stuff in, bottle after bottle, to cure an obvious leak that should be fixed, in your case Johnny i would suggest that is what happened to your car in the past.