The only thing these products do is separate you from your money. You can check to see if your head gasket is blown in several ways. One is to check if there's water mixing with the oil. The other is to remove the resevior cap (while engine is cold) and rev the engine up to at least 1000 rpms. If you see large bubbles then your head gasket is blown. There's a more sure fire way to check: Use a tester which uses a chemical to detect exhaust gases in the coolant. but most times they're not necessary.

You also need to eliminate other possible causes. The most simplest: make sure the resevoir cap is good. Because if the gasket inside is bad, it won't allow pressure to build up in the system. This will make the coolant boil. Also make sure the cooling system doesn't have a blockage. check the pump, thermostat and radiator fans as well.

Answered by Ernest Clark (expert)
1,780 answers provided