2.5L 4-Cylinder Engine Complete Assembly for 2025-2026 Subaru Forester

A quick look at your own vehicle makes sure the right engine shows up:

• Check your VIN: Look at the metal plate on your driver's side dashboard or the doorjamb sticker. Confirm that the 6th digit of your VIN is D.
• Verify your Drivetrain: Confirm that your vehicle is equipped with All-Wheel Drive (AWD).
• Confirm the Thermostat Style: Look at the cooling system on your current engine. Confirm that it uses a traditional mechanical thermostat housing rather than an electronic Thermo Control Valve (TCV) assembly.
• Visually Inspect Your Engine Bay: Take a quick look at your current engine. It should be naturally aspirated (no turbocharger). This replacement engine does not include a turbo.

What the install really takes — plan and budget with confidence:

Special tools this job needs:

• Engine hoist/crane with an adjustable load leveler
• Subaru-specific engine stand adapter (or heavy-duty universal stand)
• Torque converter holding tool or flexplate lock
• 12-point 16mm box wrench
• High-quality bidirectional scan tool
• Comprehensive metric socket set (8mm-18mm), extensions, and swivels
• Torque wrench
• Cam sprocket holding tools (e.g., Company23 brand)
• Fuel line disconnect tools
• Pliers for hose clamps

Budget for these consumables at install:

• Engine Oil: 0W-16 fully synthetic engine oil (approx. 4.4 to 4.8 quarts) [Note: sources differ on oil spec: 0W-16 vs 0W-20 - confirm with us before install]
• Oil Filter: New OEM Subaru oil filter (Part # SOA6351520815)
• Engine Coolant: Subaru Super Coolant (pre-diluted blue formula)
• Spark Plugs: Four new NGK Laser Iridium spark plugs
• Gaskets & Seals: Intake manifold gaskets, exhaust manifold gaskets, valve cover gaskets, spark plug tube seals, and a new oil pan drain plug crush washer
• O-Rings: Replace O-rings on components like the coolant crossover pipe

What your vehicle’s computers will need after the swap:

What’s involved: Crankshaft Position (CKP) Sensor Relearn, Throttle Body Idle Air Volume Relearn, CVT Transmission Adaptive Relearn, and Immobilizer Re-marriage

A professional bidirectional scan tool (or a trip to a dealership/specialist using the Subaru Select Monitor diagnostic software, specifically SSM5-R) is required. After installing the engine, you must perform a Crankshaft Position Sensor relearn so the computer can accurately monitor misfires. Additionally, because the engine was separated from the CVT, a transmission adaptive relearn must be performed to ensure smooth shifting and prevent transmission damage. An immobilizer re-marriage is also required to make the replacement engine work with your vehicle's security system.

Pro tips for a smooth first start-up — hand them to whoever does the install:

• Torque Converter Seating (CRITICAL): When you separate the engine from the CVT, the torque converter can easily slide forward off its splines. Before installing the replacement engine, you must verify that the torque converter is fully seated back into the transmission. You must spin and push the converter until you hear and feel three distinct 'clicks' or drops as it engages the pump gears. If the converter is not fully seated, bolting the engine to the transmission will crush and destroy the transmission's internal oil pump, ruining your CVT.
• Torque Converter Pin: When separating the engine from the automatic transmission, a small pin/stud from the torque converter can break off and remain in the crankshaft flange of the old engine. You MUST ensure this broken piece is not present in the replacement engine's crankshaft before installation. Attempting to install the engine with this piece in place will prevent it from bolting to the transmission correctly and can cause major damage.
• Flexplate-to-Converter Bolts: Access to the torque converter bolts is through a small opening on the top rear of the engine block, covered by a black rubber plug. You must rotate the engine by hand to install these bolts one by one. Use hand tools only; do not use an impact gun, as these threads are easily stripped.
• Boxer Width Clearances: Because of the flat Boxer design, the engine is exceptionally wide. When lowering the engine into the bay, use a load leveler and go slowly to avoid crushing the plastic valve covers or damaging the air conditioning condenser.
• Dowel Pins: Ensure the alignment dowel pins between the engine block and transmission are in their correct locations. Sometimes they stay in the transmission housing, and sometimes they stay on the engine block. Doubling them up will prevent the engine and transmission from mating.
• Harness and Manifold Swap: You will almost certainly need to swap the complete intake manifold and engine wiring harness from your original engine onto the replacement unit. This ensures all connectors match your vehicle's chassis harness and the ECU communicates correctly.
• Ground Wires: Pay close attention to all ground wire locations. There are typically grounds on the back of the cylinder heads and on the starter. Missing these can cause frustrating no-start or electrical issues.
• Accessory Brackets: Carefully compare the accessory brackets (alternator, A/C, power steering) between your old engine and the new one. While they should be the same for the identical model, it's a critical verification step.

Easy to get right once you know them:

• Double-Gasketing the Oil Filter: When removing the old oil filter, the rubber O-ring gasket frequently sticks to the engine block's mounting pad. If you spin the new filter on over the old gasket, the seal will blow out under pressure, pumping all of your engine oil onto the ground within seconds and destroying the engine. Always verify the old gasket came off with the old filter.
• Ordering for the Wrong Vehicle: Buyers often assume that any Subaru '2.5L Boxer' engine is interchangeable. This engine is highly specialized for the redesigned 2025 Forester. Ordering this unit for an older Forester, Outback, Legacy, or Crosstrek will result in a costly return, as the wiring, cooling lines, and ECU programming are completely incompatible.
• Forcing the Engine and Transmission Together: If the engine block and transmission bellhousing do not slide together flush by hand, do not use the bellhousing bolts to pull them together. Doing so will crack the engine block or destroy the transmission pump. If they do not align, pull the engine back out and re-verify that the torque converter is fully seated.
• Ignoring the Broken Torque Converter Pin: A previous installer or the salvage process may have broken the pin from the donor vehicle's torque converter, leaving a stub in the crankshaft. You must check for and remove this. If you try to force the engine and transmission together with this stub in place, you will damage the transmission, the engine, or both.
• Reusing Old Gaskets and Seals: To save a few dollars, some installers reuse old gaskets for the intake or exhaust manifolds. This is a common cause of vacuum or exhaust leaks after the swap, leading to poor running conditions and check engine lights. You must use new gaskets.
• Not Transferring the Original Wiring Harness: Buyers sometimes assume the harness on the replacement engine will be plug-and-play. Often, there are subtle differences. The safest and standard professional practice is to transfer your original engine's harness to the new engine.

Not issues with the units on this page — the manufacturer documented these for every engine of this family, wherever you buy one. Handy for your installer: