1998 Subaru motor swap


Asked by May 23, 2017 at 01:58 PM about the 1998 Subaru Forester

Question type: Maintenance & Repair

I just picked up a 1998 Subaru Forester with a 2.5l.
Knowing it has some issues with the engine I
reluctantly drove it home. Soon after doing some
research I found that the 2.5l was arguably one of
the worst engines Subaru ever made due to the
most prevalent head gasket failures, but I am still
eager to get it going simply for the 4WD as well as
my love for its body style. So the first thing I did
was remove the master air flow and checked the
spark plugs; after removing the plugs I found water
in two of the cylinders and figured that the same
thing must've happened with the gasket and just
wasn't taken care of. Then I took a look at the
thermostat only to find that the center had been
torn out; I'm guessing to accommodate for the
overheating engine. So I replaced the thermostat,
but I really didn't like the chances of putting money
into the engine when the heads were most likely
warped from overheating and not being taken care
of. After coming to this conclusion I picked up
another Subaru for its engine and plan to swap
them. This being my first Subaru engine swap I
would greatly appreciate any questions, comments
and tips that everyone has. As well as a couple
answers I'm sure I'll have along the ride. Thanks
sincerely, John

9 Answers


If you replace the head gaskets with modern multi-layer gaskets you probably won't have a problem. Look up how to do it correctly as the engine should be pulled to do it right. If the heads are warped they can be surfaced. You can swap engines if they are compatible but you don't say what year/model car your donor is.

1 of 1 people found this helpful.

If you swap engines out I would replace the head gaskets, water pump, timing belt, timing belt idler wheels and maybe the head bolts too. This work will be fairly easy with the engine out of the car.

1 of 1 people found this helpful.

The donor is a 1998 Forester as well. I'm sure every areas mechanics prices differentiate, but do you think it would be more cost efficient to resurface heads and replace head gasket or complete motor swap with other minor replacements that you mentioned? Another concern is the heads not just being warped, but if they're cracked as well..

1 of 1 people found this helpful.

Always have the heads crack tested when doing any head work, especially when you have leaks. I would evaluate both engines before deciding which engine to use. Clearly you are being smart about your project so keep researching and investigating before committing to a plan of action. If the donor engine runs well and has no obvious issues I would probably go with it.


HANG ON! The original DOHC 2.5i motor you have is FAMOUS for NOT suffering head gasket repair successfully, as the failure model is high-pressure percolation, NOT simply atmospheric leakage (like the simpler SOHC 2000-2012 motors). Too often we've rebuilt old DOHC motors to have them come apart from catastrophic rod failure within a few months of buttoning them up. Just DON'T do it! You can try the untouched replacement motor, but only if cheap and your karma protects against eventual high- pressure explosion. These first DOHC motors were too complex for their geometry and thermodynamic stresses, and should by now all be relegated to recycling. Gooid luck...but protect your pocketbook.


That may be Guru but my dad's 99 Subaru has well over 200k miles on the original head gaskets. Once I told him about Subaru anti- leak, his tiny coolant loss stopped. He does of course drive it like an old man which he his.


Isn't 99 SOHC though?


I Think some F's had the new SOHC motor, but all Legs/OBs didn't get it until '00.


99 might have been like a half-n-half kinda deal.. wonder if opposedforces would have some details regarding vin # counts, etc.

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