additives for blown headgaskets

With one minor difference, they're exactly like weight loss pills. The one difference? Some weight loss pills actually perform as advertised. Those would be the ones that require a prescription.

Things are similar for head gaskets. The only ones that work are those that you get with a prescription. And the prescription when the diagnosis is "blown head gasket" *ALWAYS* reads "New head gasket". Only a quack prescribes an additive to treat a blown head gasket.

your kidding ? if not replace it

Some outfits have a tech come along with the product and manage the process. Anyway, the worst luck seems to be fixing exhaust gas leaks into the cooling jacket, as you might expect, as the exhaust will blow the stuff out of the leak, so you're supposed to pull the plug on that cylinder; but then there's not as much heat to make the stuff harden in place. As you might guess, better luck with coolant into cylinder type leaks, for the opposite reasons of above. And there's always the chance that it will sludge up the coolant system; the manufacturers say it can't happen, but there's always some reports.

Anyway, I wouldn't mind trying it as a last ditch attempt in a car where the alternative was tossing it, but I think in a car I had hopes of keeping I would just bite the bullet and pull the head.