W
wcb
I can speak from some experience here, at least regarding the "Phase 1"
2.5L engine. I have one in my '96 Outback, and it developed the two
most common headgasket leaks at about 110K miles. Well, actually the
coolant leaking out problem developed first, on the left side, and I
was able to manage that with some Stop Leak. The second HG blew in
what I've found from my web research to be the more common failure, a
rupture in a very narrow area between the cylinder bore and a water
jacket race. Two things manifest themselves when that failure happens.
First, hot gas is forced into the water jacket, causing coolant in the
vicinity to vaporize and thus create a steam bubble. That steam
eventually percolates out past the radiator cap into your overflow
reservoir where it makes a characteristic gurgling sound. Some coolant
can also be sucked into the cylinder thru that rupture, which causes a
loss of coolant overall. Bottom line is, you think you have a coolant
leak, you keep topping off the system, and the coolant keeps
disappearing, eventually leading to engine overheating. No funny
sounds, no radical change in cold cylinder compression (so you don't
see it with the usual compression test), and nothing but the mysterious
disappearing coolant to tell you that your Head Gasket's been blown.
That's the symptom most reported by 2.5L owners.
2.5L engine. I have one in my '96 Outback, and it developed the two
most common headgasket leaks at about 110K miles. Well, actually the
coolant leaking out problem developed first, on the left side, and I
was able to manage that with some Stop Leak. The second HG blew in
what I've found from my web research to be the more common failure, a
rupture in a very narrow area between the cylinder bore and a water
jacket race. Two things manifest themselves when that failure happens.
First, hot gas is forced into the water jacket, causing coolant in the
vicinity to vaporize and thus create a steam bubble. That steam
eventually percolates out past the radiator cap into your overflow
reservoir where it makes a characteristic gurgling sound. Some coolant
can also be sucked into the cylinder thru that rupture, which causes a
loss of coolant overall. Bottom line is, you think you have a coolant
leak, you keep topping off the system, and the coolant keeps
disappearing, eventually leading to engine overheating. No funny
sounds, no radical change in cold cylinder compression (so you don't
see it with the usual compression test), and nothing but the mysterious
disappearing coolant to tell you that your Head Gasket's been blown.
That's the symptom most reported by 2.5L owners.