I know use of the stuff is controversial, looks like an easy way out, etc.

OTOH, the radiator in my '89 Chev G20 (3/4 ton van) with 305 has a tiny, tiny leak. It will go down, I'm guessing 4 fluid ounces in a day of long driving. After a few weeks of use, if unattended, will start to get badly low.

I had a devil of a time finding the leak, could never see signs of fluid leaking. The other night I started it up and let it idle for about 30 minutes. I came back out after 15 and saw a tiny puddle under the radiator. I swept that water away - it dried up and no more was added to it.

I did the same the next night, after topping the radiator again, and after 5 or 10 minutes saw fluid in the same spot. I got under and could see a small trickle coming down the side of the radiator. After it warms up, the leaking stops (!?). Probably why I couldn't find it before.

My thought is to bypass the heater core during use of the stuff as years ago with an old Dodge I think I largely plugged up the core with two applications of the stuff. I was a few hundred miles from home and it did get me home but w/o almost no heat.

My coolant mix is heavy on water at this point. One idea is to put in the Bars Leaks, run it long enough for it to do its thing, then draining most of it and putting in fresh anti-freeze and water. I think the bulk of the work is done initially - the little pellet thingies melt and go where they will but not sure I want to risk plugging my heater core (hard to replace on these rigs I've read) after I hook it back up.

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1986 300SDL, 362K
1984 300D, 138K