Duramax LLY with 170,000 miles. 2004.5 My diesel was leaking the coolant pass the rubber o-rings atop the fuel injectors. I am posting this after several hours of reading mysteries of where the coolant is going. My coolant would evaporate by the heat of the engine. A quart a week. Would anyone know how to repair the 2nd generation or newer heads? Would acidic coolant possibly be the reason for leakage into the injector passages, causing porosity in the head? Mine was flushed and changed at recommended intervals. For now I have purchased new OEM heads just to get back on the road. I could not find a after market mgf. of general heads.