Well to start I had my coolant system flushed yesturday by a dealer as I couldn't get to it myself this year. The last flush I did was 2 years ago. I'm aware of what is recommended on the board but can't see why 2 years shouldn't be enough. Two years ago everything was fine with no contamination. This year is a different story. Heavily contaminated with the grey sludge. They use a mild cleaner and did it twice! This started me to thinking. Where the hell is this sh*t coming from? It wasn't there 2 years ago at 65k. And I'd expect if it was casting sand or something left over from manufacturing I would have seen it then. This is what I've theorized. The sludge is actually carbon from the combustion process entering the cooling system. The HG fails ever so slightly and combustion/exhaust gases are forced into the cooling system and slowly start to accumilate. Just as we see carbon build up in the EGR system. This build up, if goes unchecked eventually compromises the cooling system by clogging the radiator and creates a condition that results in a catostrophic HG failure. If I'm correct then the yearly flushes are merely treating the symptom and not resolving the problem. It has been thought that the sludge was the cause of the HG failure but I'm thinking that the HG failed and caused the sludge. I have some mandatory time to take off by April and a head gasket is in order for me as I need this truck for work. Besides it will only get more costly later. What do you guys think?