Exp on HG failure

[LSiTo5Revo]

Here is some of the technical information related to the gaskets used.

In 1996 on the 2.5l engine Subaru used a composite type head gasket similar in construction to the head gaskets found in the Subaru Legacy & Impreza 2.2l engine. Starting in 1997 and used through 1999 Subaru began to use a multi layer steel shim head gasket with a graphite type outer film. And this is where the problem has started.

What we typically see with these gaskets is that the film between the combustion chamber and the cooling jacket or passageway is compromised allowing coolant into the combustion chamber and exhaust pressure and temperature into the cooling system. Subaru has come up with an updated head gasket design that seems to be holding up well.

In mid year 1998 Subaru redesigned the 2.2l and 2.5l, most of the changes were in the cylinder heads and camshaft configurations. This design has had mostly problems with external head gasket leaks. Both oil and coolant

(Here is more info from a different web site)

Subaru has also had some head gasket leakage problems on 1998 Impreza, and 2000 and newer Outback and Legacy models with 2.2L and 2.5L engines. The problem occurs on the left side of the engine and is usually an external oil and/or coolant leak. The cause may be battery corrosion (the battery is located above the left side of the engine) that attacks the outer edge of the head gasket.

Does that sound reasonable to you guys? Battery acid eating your Head gasket until it dogs you. The key word in there is "MAY" be battery corrosion. In my opinion i think that could cause some thing of that sort. But that isn't the only cause though.

[Mikey97D]

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Does that sound reasonable to you guys? Battery acid eating your Head gasket until it dogs you. The key word in there is "MAY" be battery corrosion. In my opinion i think that could cause some thing of that sort. But that isn't the only cause though.

IMO - not changing the oil often enough and gas washed oil can cause degradation of the gasket over time.

[LSiTo5Revo]

That was mentioned also.

[ouch1011]

In my experience, composite head gaskets are actually more likely to fail under the heat and pressure of combustion. Most of the engines with common head gasket failure issues used composite gaskets, and by far the most common one (the Ford 3.8 v6) actually performed a recall to replace the stock composite head gaskets with mls ones.

The original MLS Subaru gaskets were just a poor design. Combined with the fact that the sealing area between the cylinders and the coolant passages is tiny on the open deck engines, and you have a recipe for head gasket failure.

[LSiTo5Revo]

I agree with the heat and compression. To an extent. That would be like running Torco or vp 118 in any motor without internals done. You wouldn't be gaining anything but ALLOT of heat and some what a bit more compression. Which i don't i think would be much more at all. But pre-ignition also tributes so they say. so for the extra measure id go a bit higher with the quality of petrol i'm burning.