However, if there is no sign of cooling system distress, the odds are that the head gaskets have been replaced by now with the good ones and the engines will typically run 100,000 miles on these. So, if the symptoms of overheating or overpressurization are present now, then the head gasket(s) are close to or have failed. a pricey repair, especially if it was one of the early style replacement gaskets which didn't always hold up for the long term. Most dealers wouldn't even mess around with trying to save a head, they'd replace a head on any subie engine that had the gasket failure and signs of overheating. 002", so there isn't much tolerance for warping on these. But the maximum amount that can be removed off a subie head is. Subie and the aftermarket both went through several iterations of head gaskets before a sandwich style gasket was designed that minimized the failure problem. If the gasket failure was caught at the time when it started and repaired, it was possible that the subsequent damage had not yet taken place and the head could be resurfaced and reinstalled with an updated head gasket. An additional failure area was the thin wall of the cylinder in the block, which would crack. As the coolant level goes down, the cooling at the head and block doesn't happen and the heads overheat/warp/crack.
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The fire ring area of the head gasket sealing at the cylinder would blow through, so it would pressurize the cooling system, blocking coolant flow through the cylinder head/block and would blow the coolant out the radiator cap. Head gasket failures of this era in the 4-cam 2.5 liter engine were an internal failure, not an external failure item.