Drivers and auto mechanics report head gasket problems with some Subaru vehicles. The commonality of this problem falls into two groups or years of production.
The first production year group in which Subaru head gasket failure commonly occurs is the first generation 2.5-liter engine found predominantly in the 1996 to 1999 Outback, Legacy G.T., Forrester and Impreza. The second group is the second generation Subaru 2.2-liter and 2.5-liter engines found in the Forrester and Impreza from 1998 and the Outback and Legacy from 2000.
Signs of head gasket failure include exhaust, fuel or sulfur smells in the coolant overflow bottle, unusually high coolant temperature gauge readings, overheating and external oil and coolant leaks.