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Old 11-01-2012, 03:15 PM
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Originally Posted by crussell85 View Post
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?
If it's leaking internally you should see it in the oil. A pressure test of the colling system is in order to see if the system is actually leaking, if it is it won't hold pressure. A 2002 would have DexCool, this stuff can and does attack gaskets as it ages and runs out of buffers.

Before tearing the heads off a leakdown test would give an idea as to how good the rings are assuming the valves hold pressure.

Too a general extent what you mechanic is saying is that when the top end is restored to an old engine with worn pistons, rings and cylinder walls that often the result of restored pumping actions above the piston will pull oil around the worn parts and will allow more blow by into the crankcase. This depends upon the wear on those parts. If the engine isn't an oil burner today chances are good you can do the top end without introdcing any new problems. If it passes a leakdown test I don't think I'd do anything but chase and repair the coolant leak. Today's engine valves have special treatments on them that refacing the seats take off, once removed their life span will be shortened and you'll be back into the engine again and again for repairs or replacements. So I'd be cautious about just fixing things that don't necessarily need fixing because we used to do these things as a matter of course a few years ago, much has changed in recent times.

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