That stuff will gum up every little nook and cranny of the radiator, then along with fixing the head gasket leak,,he'll be pulling out the radiator to get it rodded out to get all the krap out of the radiator.

Neighbor told me about this and I was the first to think "BS" on this but this stuff DOES work and will NOT plug up the radiator.

Go to your G.M dealership, and ask for their "stop leak tablets".  There's 6 (I think) in a pack. The pack is NOT cheap. but it will stop the leak. The tablets are made out of ginsing root, and a few other goodies that will plug the "weep" but not Krap up the rest of the cooling system.  I had a tractor radiator running a stream of coolant out,, the neighbor said "here try this" and handed me a pack of those tablets. THEY WORKED!  The tablets disolved plugged the hole and I ran the tractor for months,, no LEAKS PERIOD!

A G.M. dealership is the ONLY place you can get the tablets,, but they do work.