My dealer diagnosed it initially as a bad rad cap, then a leaking crossover, then finally a bad headgasket. After $1000 worth of un-necessary repairs, the dealer openly told me they have never done a headgasket on this car, they would rather sell me a new motor. So I called one performance place that does Corvettes and puts Superchargers on trucks and such, said they have done one and will never do it again. Called another performance place and they gave me a price and told me it would be no problem. They got all the updated parts from GM, did the Time-Serts and fixed it up. 8 months later she is still going strong. The guys I brought it to are known for being quite expensive, but I would never take it to anyone else. If you get someone to do it, make sure they have experience with this motor! And make sure you do the Time-Serts!!!