While many will preach against it, I always kept the pelleted BARS-LEAK in my old 6.9 and never had a coolant leak.
When I first got the truck, it was nearly new and already had the notorious right-side rear-corner head-gasket leak.
It kept the rear corner of the engine coated with green dripping anti-freeze and left a puddle wherever parked.
Also, I constantly was plagued with that sickening sweetish smell of anti-freeze in the cab.
I made my living in this truck and was often in it for days on end.
I didn't drain anything, I just shook up TWO of the big truck-sized bottles of pelleted BARS-LEAK and dumped them in the radiator.
By the next day, the leak was gone.
About once a year, I dumped in another bottle, and never ever had another leak, and the heads have NEVER been off of that engine.
500,000-miles and the original water-pump is also still on that engine.
Beware, though, and NEVER put BARS-LEAK in any of those little anemic radiators on some of the later-model vehicles, as it will do it's job and stop up the cores in the radiator.
