The problem Troy is that "stop leak" plugs up heater cores. By their nature, that's what they do. They plug up leaks....and then they plug up heater cores.
I've seen a million people walk into my CARQUEST stores asking about "stop leak". We carry three brands or more, and the counterperson always gives them a disclaimer about plugging their heater core up....some brands of stop-leak are suspected to be worse offenders in this aspect than others, but they are all a temporary fix.
Also keep in mind the importance of completely flushing out the Dex-Cool from your system. GM is known to have added a complementary "stop leak" to some of their cooling systems that I've heard described as crushed up walnut shells. I've seen it myself in my '01 Grand Prix...it looks like crud, sediment, mud, but it's actually this sedimentary additive that Chevy added to their cooling systems in the factory. I've heard that the purpose of this stuff was to stop any leaks that may have been noticable at the dealership, in the showroom. It was sort of a last ditch additive effort to seal the cooling system before retail sale, the long term ramifications of which were not considered at the time. It's kind of a vicious GM rumor, and I can't get a straight answer from any GM people on it...but any technician can confirm it.
Also, remember that Dex-Cool is an Organic Acid Technology coolant (OAT). By nature it is aggressive and acidic. It's been known to destroy intake manifold gaskets (very common on GM vehicles from the 80s to the 90s, 4.3L Vortec, 5.0L/5.7L, and particularly the 3.1L/3.4L V6 engines of the mid 90s). Exposure to oxygen accelerates the acidic properties of Dex-Cool, so over time it becomes aggressive enough to eat through water pumps, intake manifold gaskets, etc. This is ironic, considering that GM advocates using Dex-Cool for 150k miles. So a proper flush of the system, including a backflush of the heater core is essential to limiting the corrosive effects of Dex-Cool.
Hope that helps. You're talking about a hell of a can of worms here, just watch all the Dex-Cool posts start popping up.
Mr.Clean '03 Taco
Aren't you a Regional Manager AND a little bitch?
As yet unnamed '03 Honda Shadow Sabre 1100