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Old 09-17-2012, 02:13 PM   #1
nels0300
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Default FB engine and head gasket design

I've read somewhere, can't remember, that Subaru has changed the head/head gasket design on the new FB engines. Does anyone have additional detail on this? Are they trying to address the head gasket problems that the 2.5L is having?

I didn't realize the head gasket issue on the 2.5L was so widespread until I joined this site.

I would assume Subaru would have addressed this with the new FB engines....but I also would have assumed they would have addressed the issue after a few years of the 2.5L and from what I've read, they didn't.

I understand time will tell with the FB, but I am curious to hear what the Subaru experts/techs on this site think about the FB and potential head gasket issues.
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Old 09-17-2012, 11:15 PM   #2
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Quote:
Originally Posted by nels0300 View Post
I've read somewhere, can't remember, that Subaru has changed the head/head gasket design on the new FB engines. Does anyone have additional detail on this? Are they trying to address the head gasket problems that the 2.5L is having?

I didn't realize the head gasket issue on the 2.5L was so widespread until I joined this site.

I would assume Subaru would have addressed this with the new FB engines....but I also would have assumed they would have addressed the issue after a few years of the 2.5L and from what I've read, they didn't.

I understand time will tell with the FB, but I am curious to hear what the Subaru experts/techs on this site think about the FB and potential head gasket issues.

HG's problems are so 98-04
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Old 09-18-2012, 11:56 PM   #3
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05-07 have suffered from it as well. Bloody single-layered steel gasket design on the EJ251 and EJ253, which was also very sensitive to coolant acidity. 08-11 havent yet massively reached the usual 100 000 mile mark where most issues occured, but I wouldn't expect them to be much more robust.
As for the FB25 or the FA20, no freaking clue - the oldest ones are 11' Foresters, so too low of a mileage to judge. Given an engine redesign and a well known problem I'd suspect SOJ did spend a few pennies to fix the issue.
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Old 09-18-2012, 11:57 PM   #4
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double post
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Old 09-19-2012, 01:57 AM   #5
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Quote:
Originally Posted by Bluefoton
05-07 have suffered from it as well. Bloody single-layered steel gasket design on the EJ251 and EJ253, which was also very sensitive to coolant acidity. 08-11 havent yet massively reached the usual 100 000 mile mark where most issues occured, but I wouldn't expect them to be much more robust.
As for the FB25 or the FA20, no freaking clue - the oldest ones are 11' Foresters, so too low of a mileage to judge. Given an engine redesign and a well known problem I'd suspect SOJ did spend a few pennies to fix the issue.
Not to mention Toyota has some input in its design.
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Old 09-19-2012, 07:42 AM   #6
nels0300
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There is someone at Edmunds saying the FB engine's heads have their own coolant supply and that the coolant doesn't even flow from the block to the head through the gasket. I haven't been able to verify this anywhere else though. Does anyone have a picture of the gasket or head to verify?
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Old 09-19-2012, 09:30 AM   #7
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Quote:
Originally Posted by nels0300
There is someone at Edmunds saying the FB engine's heads have their own coolant supply and that the coolant doesn't even flow from the block to the head through the gasket. I haven't been able to verify this anywhere else though. Does anyone have a picture of the gasket or head to verify?
If that is true that would be a genius solution in one sense. But I would think it would add another complexity to the cooling system like external lines and/or thermostats/valves.

And besides the coolant, there lots of external oil gasket leaks.
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Old 09-20-2012, 07:33 PM   #8
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Quote:
Originally Posted by RaceFaceXC View Post
Not to mention Toyota has some input in its design.
Toyota had nothing to do with the design of the FB.
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Old 09-20-2012, 07:40 PM   #9
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Quote:
Originally Posted by Supraru

Toyota had nothing to do with the design of the FB.
Whichever one is in the brz they had some input
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Old 09-20-2012, 07:52 PM   #10
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Quote:
Originally Posted by RaceFaceXC View Post
Whichever one is in the brz they had some input
That is the FA & Toyota designed the direct injection for that engine. That engine is also used in the JDM Legacy in turbocharged form.
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Old 09-20-2012, 08:02 PM   #11
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Do the FA and FB have different head/case designs besides dimension and displacement?
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Old 09-20-2012, 08:13 PM   #12
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the fb motor is a timing chain motor, the whole timing cover is sealed with fuji bond and there is a supplied coolant from head to head. no block interference. if you look on the drivers side head there is a plastic port ontop for coolant crossover. any tech that has gone through chain driven motor class can give a better description. if you want i can post up an assembled fb shortblock
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Old 09-20-2012, 08:16 PM   #13
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Originally Posted by RaceFaceXC View Post
Whichever one is in the brz they had some input
This is why you should not make statements if you have no clue what you're talking about.
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Old 09-20-2012, 11:12 PM   #14
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Along with the FB having a timing chain it also uses a diagonally split connecting rod allowing it to have a longer stroke. This design came from the diesel engines that Subaru has in Europe.
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Old 09-21-2012, 02:23 PM   #15
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Quote:
Originally Posted by Supraru

This is why you should not make statements if you have no clue what you're talking about.
Give yourself a pat on the back for that useful post.

I obviously have no idea about anything.
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Old 09-21-2012, 02:42 PM   #16
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Quote:
Originally Posted by RaceFaceXC View Post
Give yourself a pat on the back for that useful post.

I obviously have no idea about anything.
It was a useful post. Hopefully next time you try to make a post to act like you know what you're talking about you'll think twice so you don't look dumb. Sorry guy just the way it is. You'll learn some day.
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Old 09-21-2012, 03:51 PM   #17
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Quote:
Originally Posted by xilles
the fb motor is a timing chain motor, the whole timing cover is sealed with fuji bond and there is a supplied coolant from head to head. no block interference. if you look on the drivers side head there is a plastic port ontop for coolant crossover. any tech that has gone through chain driven motor class can give a better description. if you want i can post up an assembled fb shortblock
I however would like to see one
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