You’re absolutely spot on, Craig, although my info suggests the problems started occurring in the Outback model as early as 2000. For other Subaru models, head gasket failures have been an issue since the mid-90s. Then trade seems to think that the typical fail-point is somewhere between the 120,000km and 200,000km mark, but I’ve heard of cases of cars much younger than this suffering gasket failure.
So what causes it? Fundamentally, it was a bad design in the head gaskets Subaru was using at the time. The gaskets were a composite type, made up of thin metal sheets that were coated with a graphite-based material. Frankly, they were duds and it’s this simple fact that has caused so many Subaru owners so much grief over the years. Subaru eventually changed the design of the gaskets around 2011 and the problem just stopped.
You can spot a Subaru with a head-gasket problem a couple of ways. For a start, the failed gasket will allow coolant to escape and that will lead to the engine overheating. So, a car that runs hot after a distance is a likely suspect.
Early failures tended to allow the coolant to leak internally (where it was consumed by the engine) but later generations of the Subaru motor started to experience external leaks and these, obviously, are much easier to spot. Look for an oil leak from around the sealing surface of the head and crankcase and coolant on the ground under the car each morning.
The really weird part of all this was that Subarus tend to be otherwise very reliable and durable and, serviced correctly, can cover huge distances. But the problem was made worse by the fact that the Subaru flat-four engine actually has two cylinder-head gaskets, instead of the one of most four-cylinder engines. Replacement of the dud gaskets is the only fix and it’s quite a big – and expensive – job.