Subaru Engine Reliability: A Deep Dive

When considering vehicle ownership, the engine is undeniably the heart of the operation. Its reliability directly impacts your driving experience, from daily commutes to long-haul adventures. In the automotive world, Subaru has carved out a significant reputation for producing engines that are not only powerful and engaging but also remarkably reliable. This reputation isn't born out of thin air; it's the result of thoughtful design, robust engineering, and a commitment to quality that extends through every stage of production and, crucially, remanufacturing.

The question of whether a Subaru engine is reliable is one that many prospective buyers and current owners ponder. The general consensus, supported by numerous owner surveys and industry reviews, is a resounding yes. Subaru's boxer engine configuration, a hallmark of their design, contributes to a lower centre of gravity, enhancing handling and stability. However, beyond the unique layout, the underlying engineering and the processes used to maintain and rebuild these engines are key to their longevity.

What Makes Subaru Engines Reliable?

Several factors contribute to the esteemed reliability of Subaru engines:

• Boxer Engine Design: The horizontally opposed layout of the cylinders means pistons move towards each other simultaneously. This inherently balanced design reduces vibration and wear on crankshaft bearings, contributing to a smoother and longer-lasting engine.
• Quality Materials: Subaru consistently uses high-quality materials in their engine components, from the cast iron or aluminum block to the internal moving parts. This commitment to premium materials reduces the likelihood of premature wear and failure.
• Rigorous Testing: Like most reputable manufacturers, Subaru subjects its engines to extensive testing under various conditions to identify and rectify potential weaknesses before they reach the consumer.
• Meticulous Remanufacturing Processes: For engines that have been rebuilt or remanufactured, the quality of the process is paramount. Companies that specialise in remanufacturing Subaru engines often employ highly detailed procedures to ensure the finished product is as good as, if not better than, new.

A Look at Engine Remanufacturing: The Fraser Engines Approach

To truly understand engine reliability, it's insightful to examine what goes into rebuilding one. Companies like Fraser Engines, which focus on high-quality engine remanufacturing, provide a clear picture of the dedication required. Their multi-step process, detailed below, highlights the precision and care needed to restore an engine to peak performance and reliability, which is crucial for brands like Subaru that are known for their durability.

Step 1: Engine Block Disassembly

The process begins with a comprehensive visual inspection of the engine block for any casting defects. Each component is meticulously disassembled and inspected for damage, with the root cause of failure identified. Oil and water passage plugs are removed to ensure optimal results during thermal cleaning. For marine applications, only premium castings are selected, with replacements insisted upon for all salt-water uses. High-performance engines utilise premium cores, with no repaired castings or sleeved blocks used, thus preserving the authenticity of the original block casting through skilled craftsmanship.

Step 2: Engine Block Thermal Cleaning

Utilising a thermal cleaning system, engine parts are heated evenly throughout the chamber, preventing overheating or warping. Components are heated in an oxygen-deficient atmosphere, decomposing combustible hydrocarbons and leaving parts dry. The Ace RKE 230 oven is used exclusively for cast iron blocks, ensuring ash residue is easily removed during the subsequent stainless steel shot blasting phase.

Step 3: Engine Block Shot Blasting

A shot-blasting method employing stainless steel shot removes surface contamination like rust, creating a smoother finish. This step is vital for detecting surface and subsurface defects during quality inspection. The peening process also imparts compression strength to the metal, preparing it for preliminary defect inspection.

Step 4: Engine Block Magnafluxing

Magnetic particle inspection is used to detect cracks and imperfections in ferrous engine parts, ensuring the highest quality for cast iron blocks. Specific cleaning, testing, and defect checking processes for aluminum blocks are explained before proceeding.

Step 5: Engine Block High Pressure Wash

Aluminum engine blocks are first cleaned using the AXE SW20 OS spray cleaning system, which removes all foreign material through powerful spraying action and multi-integrated nozzles. This is a crucial step for thorough inspection.

Step 6: Engine Block Sonic Cleaning

Ultrasonic cleaning, considered the benchmark in cleanliness, is used for aluminum blocks. This method reaches inaccessible areas, breaking the bonds holding small particles to surfaces. Post-cleaning, the block undergoes pressure testing.

Step 7: Engine Block Pressure Testing

The Delta Pressure tester is employed for double-checking pinholes after magnafluxing and dye testing, ensuring the integrity of all castings used in the products.

Step 8: Engine Block Preparation

Following a complete visual inspection, minor casting defects are repaired, broken bolts are removed, threads are tapped, and gasket surfaces are repaired to minimise stock removal.

Step 9: Engine Block Machining

The RMC CNC V40 enclosed machining centre is used for precise and versatile machining. This computerised machine measures and levels blocks, determines deck heights and cylinder bore sizes, eliminating operator error. It also determines the Ra finish based on block type and gasket used, utilising CBN cutters and checking surface finish with the Mitutoyo SJ-301.

Step 10: Engine Block Rod Reconditioning

The Sunnen LBB-1600 Hone, with measuring accuracy within .0001″, is used for precision rod reconditioning and pin fitting, ensuring honed bores are equal to or better than new rods. For high-performance engines, ARP high-strength bolts and nuts are fitted prior to this step.

Step 11: Engine Block Honing

Utilising Rottler’s newest cylinder honing machine, the most accurate honing is achieved, with cylinders finishing within .0001″ roundness and straightness. This machine continuously analyses and corrects the bore, maintaining critical oil clearances and machining tolerances for evolving engine designs.

Step 12: Engine Block High Pressure Wash

After precise machining, blocks undergo a second high-pressure wash cycle to ensure absolute cleanliness for final assembly.

Step 13: Engine Block Sonic Cleaning

All parts are ultrasonically cleaned prior to assembly to ensure the ultimate cleanliness level. This method reaches every surface and internal area, providing the cleaning force required for the most stringent standards.

Step 14: Engine Block Assembly

Each assembler conducts a thorough visual inspection and measures parts for proper size. Blocks are fitted with new cam bearings, oil restrictors, relief valves, new water and oil plugs, and more. Cylinder heads are installed with new bolts and gaskets, and each cylinder’s seal integrity is checked. The final inspection by the assembly manager ensures the highest quality for the remanufactured engine.

Common Subaru Engine Concerns and Their Solutions

While Subaru engines are generally reliable, like any complex mechanical system, they can experience issues. Some common concerns include:

• Head Gasket Issues: Particularly in older naturally aspirated EJ series engines, head gasket failures were more prevalent. Modern Subaru engines have largely addressed this, but it's a point of historical note. Proper maintenance and avoiding overheating are key preventative measures.
• Oil Consumption: Some Subaru models, especially those with higher mileage or specific engine variants, might exhibit increased oil consumption. Regular checks and topping up are essential. The remanufacturing process, with its precise machining and component selection, aims to mitigate this.
• Turbocharger Wear: For turbocharged Subaru models (like the WRX and STI), the turbocharger is a vital component that requires diligent maintenance. Regular oil changes with the correct specification oil, avoiding prolonged idling after hard driving, and using quality fuel are crucial for turbo longevity.

Table: Common Subaru Engine Models and Their Characteristics

Frequently Asked Questions

Q1: Are Subaru engines expensive to maintain?
Subaru engines are generally considered to be reasonably priced for maintenance, especially when compared to some European luxury brands. Routine maintenance like oil changes and filter replacements are standard. Specific repairs, like head gaskets on older models, could be costly, but proper care can prevent many issues.

Q2: How long do Subaru engines typically last?
With regular maintenance and proper care, Subaru engines are known to last well over 200,000 miles, and many owners report reaching 300,000 miles or more. The longevity is a testament to their robust design and the quality of components used.

Q3: Is the Subaru WRX engine reliable?
The turbocharged EJ25 engine in the WRX and STI models is a performance-oriented engine. While generally reliable, it demands more diligent maintenance than naturally aspirated engines. Following the recommended service schedule, using high-quality fluids, and adopting good driving practices (like allowing proper warm-up and cool-down periods for the turbo) are key to its longevity.

Q4: What is the best way to ensure my Subaru engine remains reliable?
The most critical factor is adhering to the manufacturer's recommended maintenance schedule. This includes regular oil changes with the correct grade of oil, checking fluid levels, inspecting belts and hoses, and addressing any unusual noises or performance changes promptly. For older vehicles or those with high mileage, considering a professional engine inspection or remanufacturing service can be beneficial.

Conclusion

In summary, Subaru engines have earned their reputation for reliability through a combination of innovative design, quality manufacturing, and a commitment to durability. While no engine is entirely immune to issues, the meticulous processes employed by reputable remanufacturers like Fraser Engines ensure that even rebuilt Subaru engines can offer exceptional performance and longevity. By understanding the intricacies of their design and committing to diligent maintenance, Subaru owners can confidently expect many years and miles of dependable service from their vehicles' powerful and iconic boxer engines.