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Old 10-09-2001, 12:56 PM   #1
Patrick Olsen
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Default DOHC head gasket parts info

I recently had the head gaskets done on my 2.5GT for the 2nd time in about 6 months (about 18k miles). The first time the gaskets went I spoke to Trey Cobb about head gaskets, and he told me there were a couple better options than the 3-piece gasket that was probably originally used on my '97. However, the dealership pretty much said "It's a warranty repair, we just used what the book told us to use" so the 3-piece gaskets went back on the car.

This time, I did a bit more research with Trey. According to what Trey emailed me, there are (actually, were) 3 head gaskets:
  • 11044AA443 - DOHC single piece gasket
  • 11044AA471 - DOHC three piece (sandwich style) gasket - a solid metal core with thin, rubberish black material on each side, all held together by 3 rivets
  • 11044AA521 - SOHC single piece gasket - some sort of fibrous material with metal rings around each cylinder
The AA443 has a somewhat smaller compressed thickness than the AA471, so compression would be bumped slightly. The AA521 is even thinner, about 1/2 the compressed thickness of the AA471, but Trey said you could stack two of the AA521s if desired. Trey recommended using the AA443 or the AA521, so I put that info on the sheet when I turned my car in for repairs. Hindsight being 20/20, I should have checked the parts myself, and I probably would have found the differences I describe below and perhaps could have convinced the dealer to use what I wanted. Anyway...

When I got the car back and went to change the oil (back to synthetic) and I could clearly see metal between the block and heads, and a little tab hanging down near the front of the head with a gold rivet. What the...??!! That looks an awful lot like a 3-piece gasket I told them not to use!! So, I went back to my dealer to talk to the parts guy and found out some kinda interesting stuff.

The AA443 no longer exists. It actually superceded another gasket, AA442 (not sure what that one was), and then it was superceded by the AA471. My parts guy, Art (who I'm on a first-name basis with, so I trust him ), even showed me the printout from his parts search which showed for the AA443 "Regional/National part availability: 0 ....... superceded part no: 11044AA471". Interesting. But, Art didn't let it go at that. He made some calls and found a dealer that had the AA443 still in stock and had them ship it to him. It showed up and guess what? It looked exactly like the AA471! I didn't specifically ask Art if the package was new/unopened, but I'm assuming it was.

As for the AA521, well, it's slightly different, and this particular dealership wasn't willing to use it. A more mod-friendly dealer might not mind the differences. I need to go back to the dealer and see if I can snap some pics of the gaskets side-by-side to show the difference. From what I remember looking at them the other day, the AA471 has a clearanced semi-circle (about the size of half a nickel) at each end of the gasket; the AA521 only has the notch at one end (not sure if it was front or rear, or even what the notch(es) are supposed to clear). The AA471 also had an extra dowel pin hole in one corner; the AA521 did not have that dowel pin hole, that little corner of the gasket is just not there, so there wouldn't be any interference. (Incidentally, this missing hole was at the same end as the missing clearanced semi-circle). There are a number of other dowel pin holes still there, so that difference seems insignificant to me, and the clearanced semi-circle could easily be cut from the fibrous material of the AA521 if needed, so neither of those was a deal-breaker in my opinion. Unfortunately, the service guys didn't call me, and I don't think I could have convinced them to install those gaskets even if they had called me. This dealership is very helpful, and I trust their work, but they're pretty "by the book". Like I said, a more mod-friendly dealership, like Exeter Subaru up in NH, might not have had a problem using the AA521 gaskets, but I didn't have time to drive up there and find out.

So, that's what I know about head gaskets. I'll try to get some pictures as soon as I can to show the differences between the SOHC gasket (AA521) and the DOHC gasket (AA471).

Pat Olsen
'97 Legacy 2.5GT sedan
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Last edited by Patrick Olsen; 10-09-2001 at 01:04 PM.
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Old 10-09-2001, 03:20 PM   #2
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That is some very interesting information, Pat. Thanks yet again. I still have to try to get SOA to help me fix my problem (hope I get outta work in time). If they don't, I may just have my independent mechanic install some aftermarket copper headgaskets. Damn those DOHC engines!

Jason
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Old 10-10-2001, 12:00 AM   #3
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Thanks for the info Pat

I'm going through this right now. I just picked up my MY99-SOHC Head Gaskets today.

I am concerned about the difference in thickness between the two, but hopefully it will all work out.

I'm also replacing my 6 month old, 5k mile 3-Layer DOHC Head Gaskets.

First time they went @ 42k miles while NA. (Warranty)

Now, again @ 47K miles while Turbo'd for 3k miles. (No Warranty)

Oh Well, I'm going to my shop right now to begin pulling it apart. Looks like another late night.

-Adam
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Old 10-10-2001, 06:00 AM   #4
Patrick Olsen
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Have fun, Adam! If you get a chance and have a suitable camera, get some pictures of the DOHC and SOHC gaskets please.

Pat
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Old 08-08-2002, 10:25 PM   #5
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Reviving an old, old topic just to provide a pretty important update. Before I get to that, though, allow me to catch up a bit on old business...

First off, here are (finally) a couple pictures to compare the SOHC AA521 to the DOHC AA471:

Note that all the holes are the same, but there are the two differences I had mentioned in my original post - the extra little filled in section on the DOHC gasket in the top right corner (yellow circle), and the slightly different edge (green circles). Those differences aren't very important, and would not preclude you from using the SOHC gasket on the DOHC engine.

The most important thing is the difference in thickness - the SOHC is only about 1/3 as thick, not 1/2 as thick as I had been told by Cobb. The conventional wisdom here on the i-Club has always been, "Oh, you can use the SOHC gaskets on the DOHC engines, but you'll get about a 0.5:1 bump in compression ratio." Well, if you work the numbers, it's closer to a full 1 point bump, which is quite a bit more significant.

As for the important update, the good news is that the DOHC 2.5L gasket has been changed once again. The new part number is 11044AA610, which is a 4-layer gasket to replace the old 3-layer AA471. The AA610 gasket has a more metallic look to it than the AA471 did:


I had Cobb heads and cams installed back in early May using the new style gaskets. Since then I've put about 18,000 miles on the car, including running the Open Track Challenge (7 track events in 7 days, averaging about 70min of track time per day in 90+ deg heat). I've had zero problems thus far, which tells me Subaru has fixed the gasket problem. If the OTC didn't cause trouble, nothing will (I hope ).

Pat
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Old 08-09-2002, 01:18 AM   #6
etam
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Pat, thanks for the update!

Ernest
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Old 08-09-2002, 01:54 AM   #7
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Default Bless you my son

You have saved us all a ton of dead-ended research. We owe you a ton of gratitude (and a beer or two when we see you)

Thanks Pat!

Br, Dale
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Old 09-22-2002, 07:08 AM   #8
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Checking subaruparts.com these new gaskets cost 21.79? Is this correct? How many hours does it take to replace the headgaskets? I am very eager to get my car back on the road
How much did the bill come up to for you Pat?

Thanks

edit: When did Subaru design these new headgaskets?

Last edited by popnGEAR; 09-22-2002 at 07:15 AM.
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Old 09-22-2002, 10:03 AM   #9
Patrick Olsen
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Both times I've had my head gaskets done it was under warranty, so I don't know how much it would actually cost. When I had the Cobb heads and cams done (and got the new style head gaskets) I also had some other work done (clutch, flywheel, STi motor mounts) so again I can't give a real good price. I would say you're looking at $1000 or so, depending on what labor is where you live.

If you're taking it to the dealer to do, it's a day job. If you're going to try to do it yourself it'll probably take a couple days.

I don't know when the new gaskets were designed, but it was sometime between August 2001 (when I blew my headgaskets the 2nd time and got the old AA471 gaskets again) and April 2002 (when the Cobb stuff went on and I got the new AA610 gaskets).

Pat
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Old 09-22-2002, 10:12 AM   #10
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Is 20-30 dollars the right price for the parts?? All i need is a replacement gasket correct?
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Old 09-22-2002, 10:57 PM   #11
Patrick Olsen
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If you typed in the correct part number and they said $22 then I see no reason to second guess that. I don't have my receipt from the last job handy, so I can't tell you how much I paid my local dealer (I'm sure it was more). As for the parts required for the job, the receipt from the first warranty repair shows a list of about a dozen gaskets, seals, springs, nuts and bolts. Talk to your service or parts guys - I don't see why they wouldn't give you the proper parts list.

Pat
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Old 06-02-2007, 04:52 PM   #12
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Thanks for the information. I'm trying to diagnose my 98legacy gt ej25 problem.

Trying to open a new thread for it, but I just started so I need to make a few replies before I can open a thread
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Old 06-03-2007, 12:41 AM   #13
Patrick Olsen
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Be advised this info is almost 5 years old, and I'm almost positive is no longer correct.

Edit: Just ran the AA471 part number through www.1stsubaruparts.com and sure enough it's been superceded by AA610.
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Old 11-22-2007, 02:57 PM   #14
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The 610 gasket is the shiznit, thats for sure.
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Old 11-22-2007, 10:14 PM   #15
Patrick Olsen
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Well thank God we bumped this from 5-1/2 months ago to confirm!
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Old 11-23-2007, 06:14 AM   #16
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^hahahah.

The 642 gaskets (thinner, from STi-EJ257/EJ255) cannot be used on the 1997~1999 EJ25D. The pistons hit the head.

However, on the 1996 EJ25D...they can. I've done both before.
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Old 10-01-2009, 06:04 PM   #17
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Sorry to bump an old thread, but our '98 Legacy Outback Limited with 104k miles(we bought new) just started showing the typical symptoms. Is the "AA610" gasket still the head gasket of choice when replacing them these days?
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Old 10-01-2009, 07:10 PM   #18
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My suggestion would be to run the part number through one of the OEM parts websites - it'll tell you if it's been superceded or not.
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Old 10-01-2009, 07:34 PM   #19
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Crap......I've been going through this for my "hybrid NA build".

From what I have seen:

11044AA641 = 0.58mm/0.022"
11044AA483 = 0.80mm/0.031"
11044AA610 = 1.40mm/0.055"

I have a rebuilt STi SB with higher CR pistons & P&P DOHC NA 1998 heads, I am running the "641" HG's but have what "may" be a clearance issue that sorta sounds like a bad rod bearing.

I figured I would dump all my current info into one thread to help a future searcher.
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Old 10-02-2009, 08:14 PM   #20
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Quote:
Originally Posted by Patrick Olsen View Post
My suggestion would be to run the part number through one of the OEM parts websites - it'll tell you if it's been superceded or not.
Yup, did that and the 641 is what comes up. Was just checking here to see if there was any non oem knowledge that should be considered.
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Old 04-18-2010, 06:05 PM   #21
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Default 98 Legacy Outback - Good or Bad??

Pat-

You seem to have an extraordinary amount of knowledge on the subaru vehicles from thia time period. I am looking at buying a 98 legacy outback from a friend that has "engine problems" which I believe is this head gasket issue. So with the new gaskets and parts subaru has come out with would you recommend this as a good buy? The vehicle is in amazing shape at 120K but I am just a bt weary of this gasket issue since I read alot of forums saying these cars from 96-99 are no good. I have read all your posts and I have began to feel comfortable with this buy but just wanted to ask you since you sound experienced and knowledgeable on the topic. Thanks.
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Old 04-27-2010, 03:11 PM   #22
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Default My 99 Subaru Legacy

Well after awhile of frustrating sporadic overheating and no aparent solution I come to find out through Internet research about the defective head gaskets and the symptoms associated with it, and it described my problem exactly.
I also read on the two types of head gasket problems for phase 1 and phase 2 engines. Phase 1 being the dohc and phase 2 engines being the sohc, the simpler solution being for the phase 2 engines as it only requires an additive to the coolant to fix the external leak that head gasket caused as opposed to the internal leak the dohc gasket caused and to which no simple solution exists. This is kinda depressing because from what I know these engines can last you a good while but because of it's "Achilles" heel headgasket they fall far short of they're potential and require serious work/money to rectify what Subaru never acknowledged as a problem with the dohc 2.5 engine. I am open to any and all suggestions to getting my car fixed. Thanks
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Old 04-27-2010, 03:26 PM   #23
Patrick Olsen
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Quote:
Originally Posted by James Poitra View Post
Pat-

You seem to have an extraordinary amount of knowledge on the subaru vehicles from thia time period. I am looking at buying a 98 legacy outback from a friend that has "engine problems" which I believe is this head gasket issue. So with the new gaskets and parts subaru has come out with would you recommend this as a good buy? The vehicle is in amazing shape at 120K but I am just a bt weary of this gasket issue since I read alot of forums saying these cars from 96-99 are no good. I have read all your posts and I have began to feel comfortable with this buy but just wanted to ask you since you sound experienced and knowledgeable on the topic. Thanks.
I would say with the new style gaskets a normally driven car should live a pretty good life without having to worry about the HGs again. It seems I've read very few recurring failures using the new gaskets; mine started to leak again, but that was after a few years of use, 10s of thousands of miles, and 10-20 track days.

Quote:
Originally Posted by Seth3377 View Post
I am open to any and all suggestions to getting my car fixed. Thanks
Either find a local Subie enthusiast who's willing to help you do them yourself, or find a shop that will do them. The dealer rate is pretty expensive. With that said, I've gotten quotes from dealers that covered a pretty wide spectrum from reasonable to ridiculous, so check the local Subie dealer, too.

Pat
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Old 04-27-2010, 04:33 PM   #24
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James,
We can't judge if it's a good buy if we don't know a price.

Also be warned that if it has overheated a couple of times it's likely got warped heads. Sometimes you can resurface them and make them flat. Sometimes they are warped beyond spec. The range is pretty small.
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Old 08-28-2011, 09:22 AM   #25
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Patrick, this may seem odd, but I believe I have the classic signs of a HG problem. One thing is throwing me off track. I had the hoses, thermostat and plugs changed. And system flushed three times. Picked it up from my buddy and got it home, about a 8 minute drive. No more bubbles in the overflow tank, UNTIL, the cooling fans kicked on. Both came on at the same time, if that is supposed to happen. Then I saw bubbles, rapidly at first, but then they seemed to stop. Then about minute later, slow and steady stream of bubbles. Thoughts.
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