those kind of generic old school headgasket failure modes and are not helpful for Subaru's.Look for milky oil in the engine oil, and for oil in the coolant, and smoke when you start the car. If the fluid levels are strange, like high oil and low coolant, that is a good sign. Look for external leaks where the head gaskets are located, although rare, it is not impossible.
You are asking about headgasket issues - which are EJ25's. They have very specific headgasket failure modes depending on which EJ25 you're talking about.so im looking at a few subaru outbacks from the early 2000s and late 90s. how can i tell if the head gasket is on its way out?