Heli-coils are good but are not great. The heli-coil is just a "spring" like material and it dosn't "bite" into anything when you install it. With that said if you try to remove the drain plug with the Heli-coil chance are the heli-coil brand will come out with the plug. Also if you try to tighten the plug tight to it's torque setting you can rip the heli-coil right out and have another problem on your hands (happened to me when I tried to repair a waterpump thread) There are other better ones...I used ones from Time-sert ( http://www.timesert.com/ ) to repair the threads for my exhaust manifold bolts. They are solid inserts with a flare at one end to seat it in the metal along with teeth to bite into the metal so it dosn't come out when you try to remove the bolt...or in this case the drain plug. They have metric sizes up to M18, I don't know what the drain plug size is. Steve --- In dmcnews@xxxx, "jamesrguk" <dmc12@xxxx> wrote: > Hi, > > Try using a thread insert, I believe they are called Heli-Coils, > they are often used to replace threads in engine heads for spark > plugs . . . [quote snipped by moderator]