2.5 DOHC Head gaskets - Subaru Outback - Subaru Outback Forums
 
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post #1 of 8 (permalink) Old 04-27-2019, 11:04 AM Thread Starter
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2.5 DOHC Head gaskets

Hello,
I bought a '99 Outback with a worn clutch and leaky water pump gasket. I was looking at the head gaskets to decide if I should change them or leave them. I cant tell if they're original or not. They look copper in color and to be one single layer. What was the real fault with the head gaskets on these engines? Ive done head gaskets on a SOHC only to find out the the gasket wasn't the issue but the threads had pulled out of the block for one of the head bolts. Someone said the DOHC bolts weren't torqued tight enough but I just thought it was inferior gasket material or air getting caught in the cross over causing the engine to overheat and warp the head enough to pull threads out of the block causing the same symptoms. Thanks!

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post #2 of 8 (permalink) Old 04-27-2019, 12:20 PM
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the EJ25D were the worst, as they would leak internally causing some off and on overheats and ruin the engine in a few weeks of driving. some failed right away. and doubly sad, some people did not get the work done fast enough, then "get -er done", only to have the main bearing fail just after getting it back. (weakened from the overheating,...)....and we have had threads here from people that spent all the money they had on such work only to need the engine tore open again to get to the main bearing.

(later EJ251 SOHC were external oil leakers)

do the head gasket job on it while its apart. use EJ255 turbo head gaskets OEM from subaru = the ones that end in 642. (these are bare multi-layer steel with no crap coatings to wear and leak again).


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post #3 of 8 (permalink) Old 04-27-2019, 04:16 PM
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Originally Posted by Rhineholio View Post
Hello,
I bought a '99 Outback with a worn clutch and leaky water pump gasket. I was looking at the head gaskets to decide if I should change them or leave them. I cant tell if they're original or not. They look copper in color and to be one single layer. What was the real fault with the head gaskets on these engines? Ive done head gaskets on a SOHC only to find out the the gasket wasn't the issue but the threads had pulled out of the block for one of the head bolts. Someone said the DOHC bolts weren't torqued tight enough but I just thought it was inferior gasket material or air getting caught in the cross over causing the engine to overheat and warp the head enough to pull threads out of the block causing the same symptoms. Thanks!
It's not all that profitable to discuss why - results in a zillion ideas with no real pragmatic application considerations beyond what has been known as the best approach for almost decades now. google it and read various ideas all day long to repeat the effect of an onlilne group discussion.

Other similar EJ Subaru engines, head gasket materials, headbolts, don't have the same DOHC issues and failure modes so it's usually far too simple to try to reduce it to one metric.

resurface the heads, clean the bolt and block threads, install Subaru headgaskets on well prepped surfaces and you should be good for 100k.

H6 OBW VDC, H6 OB Sedan, Tribeca, Lifted XT6
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post #4 of 8 (permalink) Old 04-28-2019, 12:28 PM
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It's not all that profitable to discuss why - results in a zillion ideas with no real pragmatic application considerations beyond what has been known as the best approach for almost decades now. google it and read various ideas all day long to repeat the effect of an onlilne group discussion.

Other similar EJ Subaru engines, head gasket materials, headbolts, don't have the same DOHC issues and failure modes so it's usually far too simple to try to reduce it to one metric.

resurface the heads, clean the bolt and block threads, install Subaru headgaskets on well prepped surfaces and you should be good for 100k.
Actually DON'T install subaru gaskets.

https://allwheeldriveauto.com/tag/subaru-head-gasket/

Good reads

97 Outback 5MT
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post #5 of 8 (permalink) Old 04-28-2019, 12:58 PM
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Actually DON'T install subaru gaskets.

https://allwheeldriveauto.com/tag/subaru-head-gasket/

Good reads
and they sell what...= 6 star.

otherwise I think they are a nice intelligent shop

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post #6 of 8 (permalink) Old 04-28-2019, 02:23 PM
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Actually DON'T install subaru gaskets.

https://allwheeldriveauto.com/tag/subaru-head-gasket/

Good reads
Those guys know their stuff and I'd highly recommend them to anyone living around them. But, actually yes install Subaru gaskets. Those, Cometic (see below), Subaru, and (with some qualifications) Fel Pro all have similar, high success rates on properly done jobs. So it doesn't matter much but a few well known shops prefer Subaru over those, and Subaru are cheap. I use Subaru unless I need a specific thickness and then I use Cometic....like a shop i'll mention in a moment.

The site specifically avoids the OP's engine, a 1999 Outback which is not a SOHC EJ25 mentioned:
Quote:
"focusing only on the phase 2 2.5l SOHC from 1999 to 2011 in the Forester and 2000 to 2009 in the Legacy, Outback and Impreza with an emphasis on the 2005 and newer models"
More generally speaking, a well known shop owner who is a better source than the awdauto guys says:

Quote:
Six Star are just rebranded Cometic gaskets with a premium price. Nothing special about them. We occasionally use Cometics when we need a custom thickness (which is very seldom). No real complaints but honestly the 770 gaskets are as good or better than anything the aftermarket has to offer and they are cheap and readily available at any dealer. Pretty much always in stock. Made by Nippon Rienz.
Quote:
Here's the really fun part. The supplier that sells them to me at that price is the supplier that owns the six-star brand. They have all that six-star stuff manufactured and re-branded for their private label wholesale line. Head gaskets, oil filters, etc.

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post #7 of 8 (permalink) Old 04-28-2019, 02:29 PM
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and they sell what...= 6 star.

otherwise I think they are a nice intelligent shop
they do have a good reputation and know Subaru's, I would not at all want to talk them down - I don't have any real experience with them but i'm tempted to 5 star them from what I do know. That said - borrowing, rebranding, and acting like you have the magic pill that know one else knows about, putting it out there for public consumption, and ignoring comparisons to OEM, Fel-Pro, and Cometic....just misses a few things for me.

IMO - the better mechanics can talk at length about the differences between Six Star, Subaru, Cometic, Fel Pro, but as you eluded to they don't do that, and may have a conflict of interest to do so.

H6 OBW VDC, H6 OB Sedan, Tribeca, Lifted XT6
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post #8 of 8 (permalink) Old 05-14-2019, 10:22 AM Thread Starter
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Thanks for all the info! I ended up going with the Fel Pro kit since Ive had good luck with it in the past. I cleaned threads but only carbide scraped the head and block then cleaned with acetone. I think everything had been done not long ago anyways. it all went smoothly and after replacing the clutch and shifter bushing it drives great. Oh and yes, I did the timing belt and water pump as well. I like the EJ22 better for many reasons but this wont be the last EJ25D since they pop up all the time with engine problems. Next time I will follow the advice of many and use Subaru HGs, this time I was a little consumed with working on it to check back in on my post. Thanks again!
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