Difference between a 'phase 1' vs 'phase 2' EJ25 engine


Asked by Jun 02, 2015 at 07:35 PM about the Subaru Outback

Question type: Maintenance & Repair

Hello all!

I'm currently rebuilding a 1998 Subaru legacy outback DOHC 2.5 liter engine due to a
failed head gasket. During my time in both repairing the engine and divulging into the
world of the EJ25 engine, I've found myself stumped by the phase 1 and phase 2 term
associated with this engine model. I know that my 1998 engine is a phase 1, but from
what I've been reading the phase 2 appeared during the 1999 model. Possibly when
they updated the outback body design to a more curvier appeal as seen from the 2000
model up?

My questions are:

What is the difference between phase 1 and phase 2? I know the 1998 outback can
only run phase 1 with the stock wiring harness

Does this phase term refer to the heads? DOHC and SOHC

Are all 1999 subaru model phase 1? or a mix of both.

And will a 1999 phase 1 engine be compatible with my 1998 phase 1 wiring harness?

Thanks for all of your time!! It is truly appreciated

5 Answers


Hi, I have a 2010 Subaru Outback 2.5 Limited that has the phase 2, EJ25 series engine. I can't answer about the wiring harness, but, you should know that the phase 2 engines starting in 2010 had the multi layered head gaskets. This is significant enhancement over the previous years resulting in a much better system to seal up the dual heads. As you know, having two heads is a blessing and curse. As far as I know, all of these phase 2 engines had the SOHC . It wasn't until they introduced the new FB series engine and the different valve placement. Unfortunately, a lot of these newer engines burn oil. Good luck.

1 of 1 people found this helpful.

I never knew really, so I Googled>> subaru forester phase 1 2 gasket << and found these two sites: http://users.sisna.com/ignatius/subaru/headgasket.html AND http://www.smart-service.com/store- head-gaskets.html Which seems to be phase 1 DOHC and phase 2 SOHC. I don't know what all they offer anymore, I truly only follow early foresters up to about 04/05.

1 of 1 people found this helpful.
Best Answer Mark helpful

Found this for you online "The phase 1 is a DOHC engine, the phase 2 is a SOHC. It's hard to describe on a computer without showing you a pic, but probably the easiest way to spot the difference is to look at the black cam/belt covers at the front of the engine (directly in front of the radiator). The DOHC engine will have two "humps" for the camshafts, the SOHC only one."

2 of 2 people found this helpful.


1 of 1 people found this helpful.

Thank you both very much for your help and time! It is truly appreciated and you have helped me immensely with my project!

1 of 1 people found this helpful.

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