'06 Subaru Forester Head Gasket Dilemma

Am I correct in assuming the Subaru head gasket problem only applies to the opposed 4 engine? (which is the one I have). The 6 cylinder model is also opposed, is it not?

Yes, you are correct on all counts.
As far as I know, the classic head gasket issue ceased to be an ongoing problem as of the 2004 model year, but it also should be noted that the 4 cylinder engines in Legacy and Outback models were a new design as of–IIRC–the 2013 model year.

Yes you are correct as far as I know @BillRussell the Six is also a Flat arrangement and doesn’t seem to be included in the “Big Head Gasket Debacle” haha that name could go in different directions as far as meanings…but you get me


According to wikipedia, the new FB engine. "The FB has an all new block and head featuring dual overhead cams with intake and exhaust variable valve timing and a timing chain "

FB25 (2498cc), on 2011+ Forester, 2012+Legacy

They went BACK to DOHC? Crikey…just when I was getting used to the SOHC yet still 4 valve per cyl arrangement. The DOHC T-Belt job on those engines can be a Royal PIA to do sometimes. Most engines today get 4 valves per cyl into the design and only use one Cam Belt Pulley to get it done… Sometimes they all work off of one cam…sometimes the cams are chained together under the valve cover (A La VW 1.8T) I have been enjoying the single cam drive layout for some time now…seems odd they would switch back to the more parts layout. But hey whatever…I can handle either.


I know there was a claim it was fixed at various times, but problems kept occurring - I just hope our 2007 Forester avoids them. The FB engine is a major redesign, with no contact between coolant and the head gasket (there’s a separate pipe). That, combined with the switch to chains from timing belts would make 2011 the oldest Forester I’d consider.

I think the Subaru head gasket problem is rooted in the opposed cylinder arrangement.
How well do the water cooled flat Porsches hold up?

Pretty damn good I think…along with the flat 6 from Subaru…so its perplexing. They should ask for help from Porsche if the solution or reason truly eludes them…which i highly doubt… But it wouldn’t be a stretch for a company to ask Porsche’s help… Harley Davidson certainly did with the V-Rod


I don’t think it’s the engine configuration - the Subaru flat 6 doesn’t have this problem, and I’ve never read about it with the Porsche engines. The first few years do have their issue with bearings that go bad, taking the rest of the engine with them.

I’ve read (but don’t know) that the 2.5 Subaru problem was partly caused by the ‘open deck’ design, see how much contact there is between coolant and the head gasket:

The Civic of the late '70s - early '80s had an open deck block; and a rash of head gasket failures.
My '75 CVCC had a closed deck and no gasket failure, bless its rusty soul.

It doesn’t help that they use 6 head bolts per side. In the old days of retorqued head bolts and no problems to speak of the engines used 8 bolts per side. A few even older models going back into the mid 80s also used an additional 2 smaller ones on the bottom for a total of 10 per side.

Many years ago Subaru issued a TSB about head gasket failures. Their printed version was vague with the language about accountability but in more simple terms it went like this.

There have been instances of premature head gasket failures and while we feel it is not really a problem the dealer is authorized to replace the head gaskets if the customer is “insistent enough”.
Translation: Stall and obfuscate the issue unless the customer goes into a rage and then we may help out…

I’ve never felt the open block design was the cause of the problem. If the gasket replacement is done properly then the head gaskets should last the remaining life of the open deck engine.
Of course that means a surgically clean, straight block surface, clean well within tolerance cylinder head, Copper-Coated or Fuji-Bonded gaskets, and a retorque or two of the head bolts.
I’ve never had one comeback on me. Comeback being mechanicspeak for the tech eating the repair.

I’ve also never kept track but my very unscientific estimate is that the majority of Subaru heads removed are found to be warped out of tolerance which is .002 maximum. One would think that a short, stubby cylinder head on a Subaru would not be prone to warpage at all but… :frowning:

Interesting discussion. It seems from my diy’er view (really just a wild guess), from that photo like the engineers wanted to keep the engine parts equally cool as possible to avoid thermal stresses causing problem, but that made the head gasket sort of flimsy.

I want to sincerely thank everyone for the responses and advice/opinions.
It all definitely helped inform my decision.

I have decided that due to the fact that there might be other issues caused by this leaking head gasket…I am just going to replace the engine.
The used dealership I bought it from has offered to do the labor at a discounted price and has assured me that he can find me an engine with a 6 month or more warranty.
So I am taking him up on the offer.
(I think he feels bad that I am already having issues…)

Of course, he wants to see the engine first and make sure that is isn’t something he can fix for a relatively affordable price. I will update the post when I know!

Follow up question…
When I have the engine pulled, what other maintenance tasks should I also have them perform to ensure that my new engine is running with the best possible parts and stays running well for miles and miles to come?

Make sure the used engine crankshaft and camshaft seals are replaced on both ends, where applicable. If there’s some kind of bearing or bushing in the middle of the flywheel for the transmission input shaft, make sure that is replaced. And there’s probably some easily replaceable seals on the transmission.

That does look like a design prone to headgasket failures, but without seeing the mating design on the heads it’s an incomplete picture. I couldn’t find one, but I did find a photo of the headgasket. Looking at the block and the headgasket, it looks a bit weak. I suppose they probably relied on the “flash rings” to keep the combustion pressures contained, but still…

I like the old flatheads. While I recognize the inherent weaknesses of the combustion chamber including the run ins (incorrect term?) between the upward facing valves, and of the sparkplug location (off to the side in the run-ins… pardon the repeat use of an incorrect term… what IS the correct term anyway?), the chamber was totally surrounded by bolts/studs. A nice secure perimeter. I know I’m comparing apples and oranges, but please allow me the liberty. I like flatheads. :smiley:

No disrespect meant to Subies. They’ve provided AWD to the masses as well as a cool hot rod for the kids at affordable prices. Granted, the hot rod won’t set any luxury standards, but the kids they targeted really aren’t concerned about luxury… and Subie hit their target with the accuracy of William Tell.

I just looked, and it looks like the engine being used in the FRS/BRZ uses the same type of design. Hopefully it won’t be subject to similar weaknesses.

... the run ins (incorrect term?)...

Intake runners.

Screw it…throw an STi Turbo engine in it…Haven’t heard of them having Head Gasket Problems…even under lots of boost. Probably because they used Stronger Head bolts and who knows what else to bolster the engine. Thats a whole other ball of wax however…


Intake runners it is.
I knew my terminology was lacking, but for the life of me I could not think of the correct term. :blush: