Possible Theory on 2.5L Head Gasket Failures?

[mnwolftrack]

I just did the headgasket job myself on our '98 DOHC OBW and have a theory regarding at least "some" of the headgasket failures on this nasty 2.5L engine. So, I thought I'd run it by you.

 

I don't know what the original "composite" headgaskets looked like, but I do know that the headgaskets I pulled from this engine were not the original. And I know this because one of the cylinder heads had a heat tab applied to it (machine shops put these on). The headgaskets that I pulled from this motor were 3 layers and appeared to be all metal, but they were not the same as the new multi-layer-steel (MLS) headgaskets I just bought from 1stsubaruparts.com. The new headgaskets are like 5 layers of equal thickness metal. The gaskets I pulled were 3 layers, and the middle layer was much thicker. Another noticable difference was that the new headgaskets were bare metal on the surfaces with exception of a silver-like coating applied around the fire rings.

 

However, the failed 3 layer headgasket surfaces had a black (plastic?) coating over their entire surfaces. This coating was cracked/broken/absent in the failed areas. The failure occurred in the "typical" spots: the passenger cylinder head at the bottom of the cylinder walls where there are two small water ports in the head gasket. It's almost like the black coating failed and created a gap for the combustion gases to leak through.

 

Has anyone else noticed this? The cylinder heads and block surfaces were not eroded at all. If anything, they had a slight build up of carbon at the failure points just like on the tops of the pistons. I've read about other theorys on this board regarding head gasket failures including wobbling cylinders due to lack of stiffeners or supports built into the block, weak composite head gaskets, exhaust manifolds in close proximity to the bottoms of the cyinder heads and head gaskets, and more. But I wonder if this is responsible for at least some of the failures?

 

I wonder how common the type of headgasket is/was that I removed? Are these 3-layer "steel" headgaskets I removed an aftermarket brand or some sort of intermediate "updated" OEM headgasket? They didn't look composite to me. When I think of composite, I think of the graphite flakie stuff I've seen used with other headgaskets that gouges and bends real easy. To show my protest against these failed 3-layer headgaskets, I even tried to roll them up into a wad and stomp on them but was unable to do so. The middle metal layer was too thick. I had to put the headgaskets in a vice and squished them into joyful shapes (it made be feel a LOT better!).

[nipper]

I did a long post here about why they fail, its been very well documented. Use the search

 

To review, it sounds like the HG may have come from someone besides subaru. Suppliers only get the original engineering data, not the in house revisions. Aftermarket may try to reverse engineer the parts, but they don't dop any real testing of some parts (reinventing the wheel).

 

Here are some causes:

 

http://www.aa1car.com/library/gasket_failure.htm

 

nipper

[mnwolftrack]

I did a long post here about why they fail, its been very well documented. Use the search

 

To review, it sounds like the HG may have come from someone besides subaru. Suppliers only get the original engineering data, not the in house revisions. Aftermarket may try to reverse engineer the parts, but they don't dop any real testing of some parts (reinventing the wheel).

 

Here are some causes:

 

http://www.aa1car.com/library/gasket_failure.htm

 

nipper

 

How old is your post? I don't know if I've read that one, and I don't remember reading anything about the problem I found with the black material eing eroded away (but the 3 layers of steel being intact along with the head and block surfaces being good).

[nipper]

How old is your post? I don't know if I've read that one, and I don't remember reading anything about the problem I found with the black material eing eroded away (but the 3 layers of steel being intact along with the head and block surfaces being good).

 

Maybe ill try to find it later. Luckily the HG posts are thining out. They still come up time to time, but i think a lot of cars who are getting bad HG from internal leaks have been repaired. Used to be several a week came up, now we can go almost a month without seeing one. Repeats happen but thats due to buying aftermarket, or not taking the heads to a machine shop to have them resurfaced.

 

nipper

[mnwolftrack]

I see--if your post was a few years or more back, I doubt I looked back that far. I'm on dialup internet so searching is slow, and information that far back can often be outdated or no longer valid. I may have read it though. I did a lot of reading on this board before I even bought my first OBW in order to research the problems I could expect.

[nipper]

Its not that old. In the last year or so, and the HG issue has been resolved for a few years, so the information is valid. At least untill the next emissions change (and the cycle starts all over again).

 

 

nipper

[mnwolftrack]

I must have read it then. I officially joined the board in September 2006, but I reviewed the board as a guest for a while before that.

[idosubaru]

Has anyone else noticed this?

YES! actually i didn't think anything of it until i read this post. i picked up a Legacy LSi that has these style headgaskets on it and they were replaced by the dealer. when i looked at it, i thought it looked a bit different but just blew it off. i just looked up when it was replaced - January of 2003.

 

when did the "revised" headgasket come out?

 

are the phase I and phase II stock headgaskets the same?