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Old 12-26-2009, 04:10 PM
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JCL JCL is offline
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When the oil separator fails, oil can be drawn into the engine combustion chambers (via the intake), or the separator can freeze closed, which pressurizes the crankcase. In that case, the pressure blows out the weakest gasket (usually the valve cover gasket), and the oil then runs down the outside of the engine on to the exhaust manifold, where it creates a lot of smoke. Although you said you had white smoke out the tailpipe, were you stopped and looking at the tailpipe (in which case the oil was in the combustion chamber), or could it have simply been the oil on the exhaust manifold that was visible behind the vehicle as you were driving? If the latter, then I would be looking to the separator more than the head gasket.

If the head gasket is repaired (assuming it needs to be), and there is no crack in the head (if there was, you would know soon after restarting it after the repair), then the engine will be fine after the repair. The mechanic isn't saying that it will have a shorter life, simply that it may not be completely repaired if there is indeed a crack. In other words, he is warranting only his repair of the headgasket, not other damage that may still exist with the head.
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