additive plugs holes.... additive doesn't know the difference between a hole / port / tube ect... it will plug / block those openings too... other parts to cooling system = radiator.. plugged rad will overheat... not to say that a tube will block up the rad and your hosed, but it could on an older rad that already has rust floating around.... Kinda the double edged sword can help and can hurt... i've seen a guy throw 2+ tubes of that through his stuff and rad is still working, but to what avail??


Last heater core I did was on my 83 Mustang <img src="/forums/images/graemlins/ignore.gif" alt="" /> I had in high school - yes a PITA!!! and on the pass side...
maybe yours is leaking and running across something then dripping on the drivers side??