2.5 Motor--Headgasket

[Len]

Fiday night, and I am reading all the horror stories about the 2.5 head gasket. It IS scarry.

 

Is there any sort of preventive maintenance (other than not letting the engine overheat of course) that can be done to lessen the chance of head gasket failure? Are there signs that will alert one to a potential problem before it becomes an emergency? Are the replacement gaskets a better quality? Once the gasket is replaced, is that the end of the story, or will head gasket issues continue to haunt?

 

I have a '96 Outback (2.5), which I believe is referred to as a "Phase 1" when referencing the gasket. Would the stop leak coolant additive that I have read about be of any benefit to the Phase 1 motors?

 

Thanks.

[Danbob99]

Well, if you ask the subaru dealerships, they'll probably throw a cool litlte blue bottle at you that has funny red fluid with white speckles. They call it their cooling system conditioner, and its made to (from speculation at the shop) either keep your engine cooler or act as a block sealer of sorts. Didn't do any good at all on my car, but my car isn't in the recomended range of cars they suggest using it on. Might be worth a shot.

 

You'll have to refrence this one, but there are diffrent leaking points betwen the phase one and phase 2. one leaks internaly, the other externaly, i'm not sure which is which off the top of my head. but yea, just keep an eye of your temp gauge, and don't sweat it too much, i've seen them over 180k miles and stock head gaskets, you might get lucky, never now. Hope for the best, plan for the worst.

[Collins]

There's no warning when this happens.And if it happens once it will happen again.I've bought 4 subarus in a row and this will be my last one.

 

Collins

[99obw]

When the Phase I fails, combustion gasses push past the gasket and into the cooling jacket. If any sealant is in the cooling system it will be pushed away from the gasket by the escaping gasses, eliminating the possibility of a seal.

 

When the Phase II fails, pressurized coolant pushes past the gasket and out of the engine. When the coolant is pushed past the gasket the sealant is pushed into the leak, plugging it up.

 

There is basically nothing you can do to prevent Phase I failures.

[The Dude]

The engine block for the 2.5L Phase I engine is basically a bored out 2.2L block. I suspect that the engineering design for the Phase I engine called for the 2.2L block to be bored out too close to it's absolute limits. Due to variation in material and manufacturing tolerances, some of the Phase I engines were overbored. Too much metal was removed, and these engines do not have sufficient stability. So, depending where they fall on the manufacturing curve, some Phase I engines are OK, some are repairable with an upgraded head gasket and revised head bolt tightening, and some are beyond any permanent repair.

I would guess that, in general, the longer the Phase I engine goes before it's first head gasket failure, the better. I suspect that hanging a good luck charm from your rear view mirror will be as effective in preventing a Phase I head gasket failure as any other measure you might undertake.

[PAezb]

So what's the opinions on the lastest 2.5 engines in the 2004 and 2005 models? Has Subaru made the necessary design changes to the block, heads, and gaskets? What about the turbo models, etc.

 

Unless there have been significant changes to the 2.5, I can't imaging why anyone would want to take the risk with either new or used. Too bad the H6 isn't offered in more configurations, and Subaru should just drop production of the 2.5 and bring back the 2.2

[Fuji Fellow]

The engine block for the 2.5L Phase I engine is basically a bored out 2.2L block. I suspect that the engineering design for the Phase I engine called for the 2.2L block to be bored out too close to it's absolute limits. Due to variation in material and manufacturing tolerances, some of the Phase I engines were overbored. Too much metal was removed, and these engines do not have sufficient stability. So, depending where they fall on the manufacturing curve, some Phase I engines are OK, some are repairable with an upgraded head gasket and revised head bolt tightening, and some are beyond any permanent repair.

I would guess that, in general, the longer the Phase I engine goes before it's first head gasket failure, the better. I suspect that hanging a good luck charm from your rear view mirror will be as effective in preventing a Phase I head gasket failure as any other measure you might undertake.

THE DUDE,

 

Your post answered a question I've been wondering about for a while. We had the 2.2 engine, which was very reliable. Then we went to the Phase 1 2.5, which had the internal head gasket failure more. And the Phase 2 2.5 has an external HG failure mode.

 

The question I was trying to figure is, where'd they get the extra 300cc to make the 2.2 into the 2.5? Was it done by increasing the stroke or the bore, and you're saying it looks like it was by increasing the bore - to the detriment of HG reliability.

 

Are there any other big differences between the various 2.5's and the old reliable 2.2? Specifically (and I've got a reason for asking), are the water pumps and thermostats interchangeable between the 2.2 and the 2.5's?

 

James

[myles]

The engine block for the 2.5L Phase I engine is basically a bored out 2.2L block. I suspect that the engineering design for the Phase I engine called for the 2.2L block to be bored out too close to it's absolute limits. Due to variation in material and manufacturing tolerances, some of the Phase I engines were overbored. Too much metal was removed, and these engines do not have sufficient stability. So, depending where they fall on the manufacturing curve, some Phase I engines are OK, some are repairable with an upgraded head gasket and revised head bolt tightening, and some are beyond any permanent repair.

I would guess that, in general, the longer the Phase I engine goes before it's first head gasket failure, the better. I suspect that hanging a good luck charm from your rear view mirror will be as effective in preventing a Phase I head gasket failure as any other measure you might undertake.

 

OK Lebowski (sp?), what's the difference between the Phase I and II 2.5's (besides the SOHC vs. DOCH)?