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Head Gasket Problem DOHC vs SOHC


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13 replies to this topic

#1 myhilo

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Posted 04 March 2011 - 10:26 PM

All this EJ25 HG stuff, but is this only the DOHC engines? What about the EJ 25 SOHC engines, different heads so is it the same problem?

#2 davebugs

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Posted 04 March 2011 - 10:44 PM

Do some searching. Different HG problem that you can usually nurse along for a while and rarely overheat enough to damage rod bearings.


Just keep it topped up, add conditioner, etc.

SOHC's are "better but different" when it comes to HG's

#3 nipper

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Posted 04 March 2011 - 10:58 PM

Do some searching. Different HG problem that you can usually nurse along for a while and rarely overheat enough to damage rod bearings.


Just keep it topped up, add conditioner, etc.

SOHC's are "better but different" when it comes to HG's


Yes if you overheat the engine you can damage the oil depending how long you baked the engine. 2.5's have the problem vs 2.2.

#4 grossgary

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Posted 05 March 2011 - 09:08 AM

All this EJ25 HG stuff, but is this only the DOHC engines? What about the EJ 25 SOHC engines, different heads so is it the same problem?

this is covered in detail too.

SOHC EJ25's are different but have headgasket problems too. Subaru offered a 100,000 mile extended headgasket warranty campaign to some 2000-2002 models and requires a coolant conditioner added to all Phase II EJ25's - so it's well documented by Subaru and all over the subaru boards.

they both have headgasket issues but they aren't the "same" actually - they fail differently and have different symptoms.

#5 davebugs

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Posted 05 March 2011 - 09:24 AM

this is covered in detail too.

SOHC EJ25's are different but have headgasket problems too. Subaru offered a 100,000 mile extended headgasket warranty campaign to some 2000-2002 models and requires a coolant conditioner added to all Phase II EJ25's - so it's well documented by Subaru and all over the subaru boards.

they both have headgasket issues but they aren't the "same" actually - they fail differently and have different symptoms.


FYI a friend recently bought a 01 Legacy GT limited that had HG's done under warranty.

I've called me dealer about 3 2002's over the past several months - one a friend owns, y I was looking at for the fella that just got the GT. NONE of the 2002's were covered. One that a friend owns has 78 or 87k. Unfortunatley back in the day they were one of the first to need a sort block due to HG/rod bearing issues and I think they had to pay that out of pocket. So their experience with Subaru's hasn't been the best but they still like them. This 02 they just bought a few months ago. So it'll be getting HG's tiing belt, idlers, WP, you know the whole deal soon. They were kind of amazed that Subaru still had HG issues. Different but still issues. A couple bottles of conditioner hasn't helped but they are trying to limp along for another week or so.

So these friends will end up with both engine styles having HG's done!

#6 grossgary

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Posted 05 March 2011 - 10:36 AM

Subaru WWP-99 is their recall notice for the extended headgasket warranty campaign. A google search shows up to 2002 (though maybe not entirely inclusive of all years). Obviously EJ22's and EZ30's aren't going to be covered and maybe there was a change in 02 of some sort where some were/some weren't. Doesn't hurt to call and check.

some folks with 99's have had them fixed under the campaign - surely RS and Foresters with the SOHC version, not the legacys which in 99 got the DOHC.

I know your experience says 02's aren't covered, doesn't hurt to call though and check. But of course time is killing it all - it's only 8 years I think so nearly all are out of range now I guess, not sure how much flex they have in that - but they have honored warranties to some degree outside of the numbers before.

#7 myhilo

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Posted 05 March 2011 - 05:06 PM

I guess I wasn't clear, because only Grossgary answered my questions re: DOHC vs SOHC. It's as if all EJ25's are grouped together when head gasket problems are discussed. It seem to me however, that the engines have significantly different heads.

So how can I evaluate what I read, do I assume all SOHC are OK and only DOHC have a problem?

Not according to Grossgary's comment, but how can I find out more details of each type of Heads?

I've found a number of links to HG replacements, some excellent with detailed text and photos, but all seem to feature the DOHC's.

:confused:

#8 johnceggleston

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Posted 05 March 2011 - 05:53 PM

well subaru never acknowledged that there was a head gasket problem for the 96 - 99 ej25 but they apparently did with the 00? - 02?.

i'm not sure exactly what you are looking for. 96 - 02/3 the head gaskets might fail. in my opinion, the 90s are more of a risk than the 00s, but whose counting?i don't know how many versions of the actual gasket there have been, but is more than subaru wuold like to admit.

at some point before 05 they found and eliminated the problem. maybe as early as 03 depending on who you talk to.

if you are looking to buy, get a late 90s ej25 with bad gaskets and do an ej22 swap. or get an early 00s and keep the ''magic'' conditioner in the coolant. or buy one from 04 or newer.

hope this helps.

Edited by johnceggleston, 05 March 2011 - 05:58 PM.


#9 grossgary

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Posted 06 March 2011 - 08:03 AM

Not according to Grossgary's comment, but how can I find out more details of each type of Heads?


your ambiguity is the cause of your confusion, ask a more specific question than "more details". DOHC and SOHC headgasket failures are covered in depth all over the place, you can find that if you want. if you want something else then ask specifically.

#10 mikec03

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Posted 06 March 2011 - 09:03 AM

Maybe I can clear up some of the confusion. Subaru used head gaskets that had three different numbers from 00 to 09. Unfortunately, no one on the various subaru forums know the difference between them. I know because I have tried very hard to find out. The last gasket [11044AA633] which was installed starting around Nov. 05 is now used as a replacement for ALL NA SOHC engines 00-99.

Unfortunately, many of the cars with this OE gasket have failed which you can confirm using the search engine. Furthermore, even though this time period included the use of three different engine models, the fact that the same head gasket can be used in all of them indicates that there is not significant difference between the engines in regard to the structural strength at the block and head connection.

PS the 633 gasket is a single metal sheet with a thin, hard black coating on both sides.

#11 Mike104

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Posted 06 March 2011 - 10:16 AM

The OPs question asked the differences between DOHC vs SOHC HGs.

The DOHC was the Phase 1 2.5L and tended to have internal HG leaks from the engine exhaust gases into the cooling system resulting in the coolant being discharged out of the overflow bottle and causing overheating. Expensive fix if you have to pay someone to do it and if the engine is overheated severely can result in damage to the engine bearings etc, resulting in rod failure after replacing HGs.

The SOHC was a Phase II 2.5L and tended to have external HG leaks of coolant or oil and the Subaru Coolant Conditioner was specifically called out by Subaru to reduce the coolant leaks. If the coolant level gets low (because its not checked by the driver) this can cause the engine to overheat.

As to when the problem was "fixed" I can't really say. The 633 P/N is the latest P/N available from Subaru (all others are superseded). Some have said good quality repair with newest OEM HGs are fine, others have said swap the 2.5L with a 2.2L.

The 2.2L engine does not exhibit a similar frequency for HG failure, but it can happen on any engine.

Here is some info http://www.subaruhea...t.com/index.htm

Subaru did change the gasket design for the 2010 model:

http://allwheeldrive...r-the-2010-25l/

#12 myhilo

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Posted 09 March 2011 - 02:02 PM

Thank you all for the replyes. Mike104's reply did address my question the most thoroughly. Which leads to another...

So, none of the ej25 are without head gasket problems compared to the older ej22.

So how does one go about finding a ej22 to use for a swap.

1) buy JDM engine?

2) buy whole car from cl w/ ej22?

3. buy junk yard ej22? and run, rebuild ???? ( the warranty on junk yard engines may be so short I couldn't get it installed and debugged before a the warranty has expired.)

4. better idea?

#13 Mike104

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Posted 09 March 2011 - 02:24 PM

Some here use local junkyards or you can always search here:

www.car-part.com

The 2.2L swap only really works for the 95-99 ish cars without too much difficulty.

Probably best to do a timing belt/reseal job on the engine going in to give maximum life.

#14 grossgary

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Posted 09 March 2011 - 02:36 PM

the 2.2's are so robust that if you get one in good running condition they're easy to keep that way. timing belt and timing components replaced - reseal it with new cam/crank/oil pump seals and valve cover gaskets and run it a long time. they're so cheap that it's not hard to find one usually.

rebuilds are generally cost prohibitive, easier just to get a known good engine.




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