I have used Barrs Leaks since the 1950's in everything from a '37 chevy to a '99 Peterbilt. The instructions are on the bottle and should be followed closely. They aren't merely suggestions. It will take a few minutes to seal the leak but will last a long time. It is not cheap as compared to other stop leak products but it is worth the expense. The soluble oil the pellets are suspended in has some side benefits to your other cooling system components as well.
Smilinjak