Stuff like Barsleak or any other stop leak product will do nothing to repair the problem. I tried to use that stuff on my old Mazda and learned the hard way.
Spend the money, your cooling system is one of the most important components for your cars engine. If you don't, your next post might be in search for a new cylinder head to replace your warped one PLUS a radiator!!!
(Which was the exact reason why I had to get rid of my MX-6...)