[HTi]Johnson Posted March 8, 2007 Share Posted March 8, 2007 Why do they fail? I know this has been asked a lot. I have read a lot of replies. Is it just the first DOHC version or did they fix it by closing fixing the Piston "Islands"...making it so it wasn't almost a solid coolant jacket around the cylinder? Some say it's because the only connection points for the cylinders were on the 3 and 9 o' clock positions. They say that the cylinder vibrate too much and cause the gasket to "wear" out. I guess my question is, would it be worth it to weld a piece of material so the cylinder is supported at the 12 and 6 position too? I've heard of a sand rail company that does that. They weld a piece in. Quote Link to comment Share on other sites More sharing options...
nipper Posted March 8, 2007 Share Posted March 8, 2007 Johnson']Why do they fail? I know this has been asked a lot. I have read a lot of replies. Is it just the first DOHC version or did they fix it by closing fixing the Piston "Islands"...making it so it wasn't almost a solid coolant jacket around the cylinder? Some say it's because the only connection points for the cylinders were on the 3 and 9 o' clock positions. They say that the cylinder vibrate too much and cause the gasket to "wear" out. I guess my question is' date=' would it be worth it to weld a piece of material so the cylinder is supported at the 12 and 6 position too? I've heard of a sand rail company that does that. They weld a piece in.[/quote'] no. i am not going to repeate myself after many many detailed posts about this (i get tired of typing). First problems is welding steel to alumunum or aluminum to steel. Then you have to anneal the metals to get rid of the stresses. Second problem is that it is not just one factor, but several that cause this. Piston islands? Learn the norminclature. I think you are talking about open deck vs closed decks. There are places that will do this and do it properly using aluminum and then machine the new deck. The problem is the open deck, or the hybrid open deck, and the limits of the technology at the time. HG is the most difficult part of the engine to design and make work. Open deck looks good on paper for perfomance and emissions, in practice its not that easy. Since 2003 The HG issue has disapeared (so far), and very few people have the HG failure a second time (not including old age). Also with emissions getting so tight, having uneven heating or cooling in the cylinder can throw off emissions and cause ping. I think it took subaru (along with other Mfgs) a while to get it right. Its just easier to replace the Headgasket with the newest HG then to go through all that trouble. I am sure in the future we will go through this learning process all over again when they tighten emissions even more. nipper Quote Link to comment Share on other sites More sharing options...
Manarius Posted March 8, 2007 Share Posted March 8, 2007 I always thought it was just that the first HG's were poorly designed and caused problems in 10 - 15% of cars equipped with the DOHC 2.5. Quote Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted March 8, 2007 Author Share Posted March 8, 2007 ...Piston islands? Learn the norminclature. ... nipper No need to be rude about it. Yes I was talking about the decks. I wasn't talking about welding steel to aluminum...as far as I know, that's impossible. I was asking if it's worth it to weld aluminum to the cylinder and add stability. But forget I even asked. Mods, delete this post please. Quote Link to comment Share on other sites More sharing options...
The Dude Posted March 8, 2007 Share Posted March 8, 2007 You pose a very interesting question. Since Subaru has never admitted to a problem with the Phase I , they have never disclosed the "fix" supposedly incorporated into the Phase II. In other words, as far as Subaru is concerned how can there be a "fix' if there never was a problem that required fixing? Even with the early Phase II engines which suffered from external head gasket failures, Subaru announced only that "counter measures" have been taken. "Counter measures" could be just about anything. Who knows, maybe one of the assembly workers in Guma spits on the head gasket before the head is installed and that's the "countermeasure". My guess, is that the latest revision head gasket that is able to accommodate a great deal of cyclinder wall movement is 90% of any real fix. Perhaps Emily from CCR or someone else with a lot of engine tear down experience can tell us if there is any real difference in cylinder wall support between the Phase I and Phase II engines. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted March 8, 2007 Share Posted March 8, 2007 there was a recent thread about this, very informative with pictures, partly written by a shop owner who rebuils / replacxes heads and gaskets, and it had a 5 star rating. i'm sure there are questions that were not asked, but i now know more about heads, gaskets and open decks than i knew to ask. it is not as simple as ... "the head gasket was poorly designed and they fixed it". http://www.ultimatesubaru.org/forum/showthread.php?t=70759&highlight=head+gasket Quote Link to comment Share on other sites More sharing options...
nipper Posted March 8, 2007 Share Posted March 8, 2007 Johnson']No need to be rude about it. Yes I was talking about the decks. I wasn't talking about welding steel to aluminum...as far as I know' date=' that's impossible. I was asking if it's worth it to weld aluminum to the cylinder and add stability. But forget I even asked. Mods, delete this post please.[/quote'] wasnt being rude, just cranky from a gallstone :-\ sorry if it came across as rude. nipper Quote Link to comment Share on other sites More sharing options...
forester2002s Posted March 8, 2007 Share Posted March 8, 2007 Johnson']Mods' date=' delete this post please.[/quote']No, please don't delete any of Nipper's posts. Nipper is of the few whose opinions I trust. Quote Link to comment Share on other sites More sharing options...
The Dude Posted March 9, 2007 Share Posted March 9, 2007 I would agree. Nipper is very knowledgeable and helpful. His posts are always welcome. Quote Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted March 9, 2007 Author Share Posted March 9, 2007 No, please don't delete any of Nipper's posts.Nipper is of the few whose opinions I trust. I meant my thread. Not nipper's post. Sorry for taking it the wrong way nipper. It's all good. Quote Link to comment Share on other sites More sharing options...
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