looking for some help with my 2011 siverado 4x4 with 6.2l. At around 70k mi the engine started to develope a noticeable tick at start up when the outside temps were 40 degrees and lower. I brought it in to a dealer and they said it was probably just carbon build up on the lifters, they ran a cleaner through it with no improvements. I brought it to another dealer a few months later and they said there was a service bulletin out and there was no action needed with this issue. The "tick" noise gradually became more pronounced into a knocking sound that did not go away once engine warmed up. At this point my factory warranty ran out but I still have an extended warranty on it but I needed to authorize them to tear apart motor in hopes that they would find something wrong internally for warranty to cover it. They found all piston skirts scuffed/scorched with cyliders 2and 7 being the worst. Warranty place would only cover fixing motor with new pistons, rings, and bearings. The rest of the motor looked good according to mechanic. This was taken care of in june 2016, truck ran fine with no noise or any issues. 11k miles on it and ticking sound is back and gradually getting worse as outside temps continue to fall here in Wisconsin. The ticking/knocking sound is at startup after truck has been sitting over night and goes away once truck is warmed up and driven for a few minutes. I've been back to the dealer that did the engine work and they are hiding behind that same service bulletin for carbon build up on lifters and that it states there is "no action" required. I only have 300miles left on extened warranty and im not getting anywhere with the dealer. I am not sure on my next course of action, any advise is greatly appreciated. thanks.
