2024-2025 Subaru Ascent 2.4L FA24F Turbo: Problems, Identification, and Used Replacement

Vehicle Fitment and Identification

This used engine assembly, part of the Subaru FA24F family, is specifically configured for the 2024-2025 Subaru Ascent. The FA24F is a 2.4-liter, horizontally opposed (Boxer) four-cylinder engine featuring direct injection and a turbocharger. While Subaru uses the FA24F engine in other popular models like the WRX, Outback XT, and Legacy XT, those versions are not directly interchangeable with the Ascent engine due to differences in wiring harnesses, accessory mounting, and engine control unit (ECU) tuning.

To confirm this is the correct engine for your vehicle before purchasing, follow these steps:

• Check the VIN: The most reliable method is to check your vehicle's 17-digit Vehicle Identification Number (VIN). The 6th digit of the VIN for an Ascent with this engine must be 'A'. You can find the VIN on the driver's side dashboard (visible through the windshield) or on the sticker in the driver's door jamb.
• Verify the Engine Code: Look for the engine identification code, which is typically on a sticker or plate on the driver's side strut tower in the engine bay or stamped on the engine block itself. Confirm the code is FA24F (sometimes identified as FA24DIT).

Common Failure Symptoms

An engine nearing the end of its life or experiencing a major failure will typically show several clear symptoms. If you experience any of the following, it is crucial to have your vehicle inspected by a qualified technician immediately to prevent further damage.

• Engine Knocking or Pinging: Loud metallic sounds from the engine bay, often described as rod knock or tapping, can indicate severe internal problems like crankshaft bearing failure.
• Excessive Oil Consumption: Needing to add oil frequently between changes can be a sign of worn piston rings or leaking seals.
• Loss of Power and Rough Idle: A noticeable decrease in acceleration or a shaky, inconsistent idle can point to a variety of internal engine issues, including compression loss or carbon buildup.
• Check Engine Light: While many issues can trigger the check engine light, codes related to camshaft/crankshaft correlation (e.g., P0016, P0017) or low fuel pressure can signal serious engine trouble.
• Metal Shavings in Oil: Finding metallic particles in the engine oil during an oil change is a definitive sign of internal components grinding against each other, indicating catastrophic failure.

Diagnostic Flowchart

Known Problems, Recalls, and Technical Service Bulletins (TSBs)

The FA24F engine platform has been in production since 2019 and has several documented issues. While many of these affect earlier model years, it is important to be aware of them as they may apply to the broader engine family. Always have a technician check for open recalls on your specific vehicle.

Recalls

Technical Service Bulletins (TSBs)

Community-Reported Issues

• Excess RTV in Oil System: A widely discussed issue on FA-series engines is the excessive use of Room Temperature Vulcanizing (RTV) sealant on the oil pan and timing cover from the factory. Pieces can break off and clog the oil pickup tube screen, leading to oil starvation and catastrophic engine failure.

• Oil Leak into Wiring Harness: A severe issue where a failed O-ring on the oil level sensor allows oil to wick through the main wiring harness, potentially destroying the ECM and causing widespread electrical damage.
• Oil Pan Gasket Leaks: Leaks from the oil pan sealant are common. It is best practice to reseal the oil pan with a quality liquid gasket (like ThreeBond 1217H or equivalent) while the engine is out of the vehicle.

What's Included in a Used Assembly?

A used engine assembly is typically sold as a "long block" with some accessories. Based on industry standards (ARA URG), you should expect the following:

Installation and Post-Install Programming

Installing this engine is a complex job best left to professional technicians with Subaru-specific experience. DIY installation is considered Expert-level only.

• Labor Estimate: Expect a professional shop to quote between 14 and 20 hours of labor.
• Special Tools Required: The job requires a Subaru Engine Stand Adapter, Crankshaft Pulley Wrench, fuel line disconnect tools for high-pressure direct injection lines, an engine hoist, an engine stand, a comprehensive metric socket/wrench set, and torque wrenches.
• Programming Required: After installation, several relearn procedures are mandatory for proper operation. These include a Throttle Body Calibration / Relearn, Crankshaft Position (CKP) Sensor Relearn, VVT (Variable Valve Timing) / AVCS Learned Values Reset, and Idle Air Volume Relearn. A dealer-level scan tool (SSM4) is highly recommended, though some high-end aftermarket tools may perform these functions.
• Consumables Needed: 4.8 quarts of SAE 0W-20 Full Synthetic oil, a Genuine Subaru 'Black' oil filter (Tokyo Roki), Subaru Super Coolant (blue, pre-mixed), OEM Subaru/NGK Laser Iridium spark plugs (ILKAR8H6), intake/exhaust/turbo gaskets, liquid gasket (ThreeBond 1217H), and accessory belts.

Installation Gotchas

• Torque-to-Yield (TTY) Bolts: The harmonic balancer (crankshaft pulley) bolt and the flywheel/flexplate bolts are torque-to-yield and must be replaced with new OEM fasteners. Do not reuse them.
• Rocker Arm Displacement: If you remove the camshaft carriers or valve covers for any reason, be extremely careful. The rocker arms on the FA24 are not physically secured to the pivots and can easily fall out of place into the oil galleries.
• Ground Straps: Pay meticulous attention to all engine and transmission ground straps. Missing or poorly connected grounds are a common cause of bizarre electrical issues, no-start conditions, and sensor errors after an engine swap.
• Fragile Sensors and Connectors: The plastic connectors for sensors and the wiring harness can become brittle with heat and age. Handle them with care to avoid breakage.
• Harness Compatibility: The engine wire harness must match the Ascent's specific model year. Transferring your original engine harness is highly recommended to ensure full compatibility with the vehicle's electronics.

What Fails at Every Mileage Band

Under 60,000 Miles

Engines in this band are relatively fresh, but early-life issues can still be present. Oil pan leaks due to failing factory RTV sealant are a common warranty claim. A critical failure involves an oil leak from the oil level switch O-ring, which can wick into the main wiring harness, causing catastrophic electrical damage (TSB 02-190-22R). Some early models also faced recalls for faulty PCV valves and low-pressure fuel pumps.

• ✓Do during install (required): Reseal the lower and upper oil pans. Clean all surfaces meticulously and reseal them using a high-quality liquid gasket (e.g., ThreeBond 1217H). Drop the lower pan to inspect and clean the oil pickup tube screen of any excess factory RTV.
• ✓Do during install (recommended): Update the PCV system. Ensure the latest-design PCV valve and hoses are installed (TSB 11-204-23) to prevent oil consumption.
• ✓Cheap insurance while the engine is out: Replace the oil level switch O-ring. This low-cost preventative measure can prevent a five-figure repair associated with oil wicking into the wiring harness. Consider installing an Air-Oil Separator (AOS) to reduce future carbon buildup.

60,000 - 100,000 Miles

At this stage, carbon buildup on the intake valves becomes a more prominent issue, potentially causing rough idle and hesitation. Oil pan leaks persist if not previously addressed. Catastrophic engine damage from a failed O-ring seal has been reported in this range, requiring engine removal and alternator replacement.

• ✓Do during install (required): Perform all 'Under 60k' tasks, including resealing the oil pan and replacing the critical oil level switch O-ring.
• ✓Do during install (recommended): Perform an intake valve cleaning. With the engine out, this is the ideal time to perform a walnut-blasting service to remove carbon deposits from the intake valves and ports. Replace the spark plugs (OEM ILKAR8H6), as this is a difficult job with the engine in the car.
• ✓Cheap insurance while the engine is out: Service the cooling system. Replace the thermostat and thoroughly inspect all coolant hoses for swelling or softness, replacing as needed. Replace the PCV valve if not done previously.

100,000 - 150,000 Miles

Problems in this mileage range are most often the result of deferred maintenance. Turbocharger wear becomes a higher probability, and standard wear-and-tear items such as drive belts, engine mounts, and coolant hoses are more likely to require replacement.

• ✓Do during install (required): Perform all lower-mileage tasks. This includes a full carbon cleaning, spark plug replacement, PCV system overhaul, and a complete oil pan and O-ring reseal.
• ✓Do during install (recommended): Inspect and potentially replace the turbocharger. If the original engine failed catastrophically, the turbo is likely contaminated. Even if not, consider replacing the turbo's center housing rotating assembly (CHRA) as preventative maintenance.
• ✓Cheap insurance while the engine is out: Proactively replace the serpentine belt, water pump, thermostat, and all major coolant hoses.

Beyond 150,000 Miles

Engine longevity is almost entirely dependent on the quality and frequency of previous maintenance. With diligent maintenance, the FA24F can reach 200,000 to 250,000 miles, but turbocharger failure is a significant possibility at this stage.

• ✓Do during install (required): Mandatory turbocharger replacement. Do not reuse a turbocharger at this mileage; install a new or professionally remanufactured unit. Perform all lower-mileage tasks (carbon cleaning, spark plugs, PCV, water pump).
• ✓Do during install (recommended): Full engine reseal. Replace all accessible gaskets and seals, including valve cover gaskets, front crank seal, and rear main seal.
• ✓Cheap insurance while the engine is out: Inspect the timing system. While the chains are designed to last the engine's life, check them for stretch and inspect the plastic chain guides for any signs of cracking or wear.

Real Owner Experiences

The following table compiles real-world reports from Subaru Ascent owners regarding engine issues, repairs, and associated costs.

Repair or Replace?

Deciding whether to repair your current engine or replace it with a used assembly depends heavily on the type of failure and the associated labor costs. Engine replacement is a significant investment, with shop labor alone running $1,800 to $3,500.

When Repair Makes Sense

• PCV Valve Failure / Clogged System: This is a cheap ($100 - $200) and critical preventative maintenance item. Always repair this before it leads to seal failure.
• Fuel Injector Failure: If only one or two injectors are faulty, replacing them ($300 - $1,500 per injector) makes sense.
• Minor Oil Pan Gasket Leaks: If the leak can be addressed without full engine removal, expect to pay $800 - $1,500. However, if the engine must be removed for access or resealing, quotes can reach up to $8,000+, making replacement a consideration.
• Head Gasket Failure: Costing $2,000 - $3,500+, this repair makes sense only if the rest of the engine (block, rotating assembly) is in excellent condition.

When Replacement is the Smarter Choice

Replacement is typically the smarter choice in cases of catastrophic internal failure. If your engine has rod knock, crankshaft bearing failure, severe oil starvation from RTV clogging the pickup tube, or a cracked block, the engine is done. Furthermore, if repair costs—especially when combining multiple issues like head gaskets and timing components on a high-mileage engine—approach or exceed 50-60% of the cost of a quality used replacement engine (used units typically run $3,600 - $4,700, while remanufactured units run $4,500 - $5,600, and new OEM units exceed $8,000 - $10,000+), replacement becomes the more financially sound option.

Questions to Ask Your Installer

Before handing over the keys, ensure your mechanic is prepared for this specific swap by asking:

• Have you inspected and cleaned the oil pickup tube screen for RTV debris?
• Will you be transferring my original, known-good engine wiring harness?
• What is your procedure for flushing the oil cooler and turbocharger oil lines to remove contaminants from the previous engine failure?
• Do you use new, torque-to-yield bolts for the flexplate and harmonic balancer?
• Are you familiar with the required ECU/PCM relearn procedures for the throttle body, crankshaft position sensor, and VVT/AVCS systems?
• What brand and weight of oil and coolant will you be using for the initial fill?
• Does your quote include replacing common wear items like spark plugs, the PCV valve, and relevant gaskets?
• How do you handle potential issues with brittle plastic connectors and ground straps during the swap?

Freight and Delivery Reality

Buying a complete engine assembly is not like ordering a standard auto part. This FA24F engine assembly weighs approximately 475 lbs and measures roughly 40" x 40" x 38" before crating. It ships as Less-Than-Truckload (LTL) freight strapped to a pallet—it is NOT a parcel delivery.

Because of its size and weight, delivery requires a freight truck equipped with a liftgate if you are shipping to a residential address or a shop without a loading dock. Industry best practice dictates a pre-purchase verification interview to confirm your VIN and fitment before the engine ever goes on a truck. When the engine arrives, you or your mechanic must thoroughly inspect the unit for any shipping damage before signing the driver's delivery receipt. Signing without noting damage can void freight insurance claims.

Before the First Start: Priming and Fluids

Used engines sit on warehouse shelves without fluids. Over time, all the oil drains down to the bottom oil pan. If you start the engine dry, the metal parts will rub together and cause instant damage. You must prime the engine first. Priming means pumping oil through the engine before it actually runs.

Mandatory Fluids

Before priming, you must fill the engine with brand-new fluids. Never reuse old oil or coolant.

• Engine Oil: Fill the engine with fresh 0W-20 full synthetic motor oil. Look for the API SP or ILSAC GF-6A rating on the bottle. This specific oil protects the turbocharger from extreme heat.
• Oil Filter: Install a brand-new OEM (Original Equipment Manufacturer) Subaru oil filter.
• Coolant: Fill the cooling system with Subaru Super Coolant (Blue). You can also use an equivalent 50/50 premixed blue coolant made specifically for Asian vehicles.

Oil Priming Procedure

1. Disable the fuel system: Open the fuse box and remove the fuel pump fuse. This stops the engine from getting gas so it will not actually start.
2. Crank the engine: Turn the key or press the start button to crank the engine for 10 to 15 seconds.
3. Let the starter rest: Wait 30 seconds so the starter motor does not overheat and burn out.
4. Repeat: Crank the engine again for 10 to 15 seconds. Watch the dashboard. Stop when the red oil pressure warning light turns off. This means oil has successfully reached the top of the engine and the turbocharger.
5. Start the engine: Put the fuel pump fuse back in. Start the engine normally. Let it idle (run without pressing the gas pedal) for 10 to 15 minutes while you check underneath for any oil or coolant leaks.

Frequently Asked Questions