I'm sure you are having the same problem as almost everyone else has had. It can be fixed in one day or less, and won't come back for six or so years.
You need to replace all the plastic cooling system parts.
Please give the year of your LS, engine (V6 or V8), and the circumstances that it overheats in, if you really want help. If you want quicker help, then just search this forum. It has been covered hundreds of times.