A thought came to me while I was sitting here thinking about my 03 GMC Sierra with 120k sitting in the shop getting the injectors replaced, I have been having to add a little water about once a month to the cooling system after doing some serious pulling (loaded to 21600) any idea if the two could be connected?:confused:

There is an injector sleeve that separates the injector itself from the coolant passages in the head. Cracked sleeves commonly go along with injector failure. Did you have white smoke coming out the tailpipe? If-so, this is coolant leaking down into the cylinder, probably from a sleeve that's failed. The sleeves are commonly replaced along with injectors, but it's worth checking with your dealer to be sure.