[lts70]

Also, Alot of time when people have this problem it is because they are over filling thier radiators. These trucks did not come with external overflows therefore you have to account for expansion in your radiator. There should be a fill line on your radiator about 3 iniches below your radiator cap. If you are filling it above that line it will push all of the fluid above that mark out and alot of times more that is below the line even as it creates a syphon. If you have been filling your radiator all the way up and dont want an external tank you might give just filling it to the line a try.