I have a 2002 Impala with the 3.8 v6. The car has 298,xxx miles on it. Recently I've been losing antifreeze somewhere internally, I don't see it leaking externally. I was contemplating rebuilding the top end. When I told the guy at the machine shop what I wanted to do he said in his experience with that many miles after rebuilding the top end the piston rings like to come unseated and sometimes break due to the additional compression and the top end being more efficient. Does anyone agree with this? And is there any way to check if its just the intake gaskets giving me the problem without tearing it apart?