What causes Subaru bearing failure?
In Subaru vehicles, bearing failure is typically driven by lubrication problems (low oil or blocked passages), overheating, and wear over time, with engine bearings most affected; wheel bearings fail due to contamination, damage, or fatigue and can mimic engine bearing symptoms.
Understanding the problem
Bearings are the heart of rotating components in engines and driveline. When they fail, the symptoms can range from knocking noises to loss of oil pressure. The Subaru boxer engine design has particular vulnerabilities tied to oiling routes, heat management, and long-term wear, while wheel bearings face different failure modes that can produce similar warning signs.
Engine bearings: what fails and why
Below are the most common contributors to crank/main/rod bearing failure in Subaru engines, based on service history and reported failures across model years.
- Low or no oil pressure due to oil starvation from low oil level, pump failure, or blocked passages.
- Oil pump failure or restricted suction causing insufficient oil delivery to bearings.
- Clogged oil passages or sludge buildup restricting flow to critical bearings.
- Overheating or thermal stress degrading bearing materials and clearances.
- High-mileage wear: normal wear of bearing shells and journals leading to clearance increase and noise/low oil pressure symptoms.
- Incorrect oil viscosity or use of suboptimal oil leading to inadequate lubrication film, especially in cold starts or high-load driving.
- Detonation, aggressive engine timing, or poor fuel quality increasing bearing loads and wear.
- Improper engine rebuilds or incorrect bearing clearances during assembly, which can accelerate wear or fail prematurely.
- Manufacturing defects or quality issues in rare cases.
Maintaining correct oil level, using the manufacturer-recommended oil grade, and performing timely oil changes with clean filters are key steps to minimize these risks.
Wheel bearings and other rotating bearings
Wheel bearings and other rotating components can fail due to different pathways, including environment exposure, load, and contaminants, which can produce noise or vibration distinct from engine bearing issues.
- Contamination or water intrusion causing seal failure and corrosion of bearing surfaces.
- Lack of lubrication or degraded grease due to long service intervals or leakage.
- Damage from impacts, potholes, or curb strikes affecting race or ball/roller elements.
- Fatigue from mileage and cyclical loading leading to bearing wear and eventual failure.
- Improper installation, incorrect torque, or variability in wheel hub assembly affecting bearing preload and life.
- Seal failure leading to grease loss and accelerated wear or noise.
Preventive practice includes regular inspections, addressing unusual wheel noise promptly, and replacing bearings as recommended by mileage or service intervals.
Preventive steps for Subaru owners
Practical steps Subaru owners can take to reduce bearing failures span maintenance, driving habits, and proactive checks.
- Follow the manufacturer’s service schedule and use the recommended oil viscosity and quality; replace oil filters at every change.
- Maintain proper oil level and promptly address oil leaks or consumption issues.
- Keep cooling system in good order to prevent engine overheating, including radiator, hoses, and coolant; fix leaks promptly.
- Avoid prolonged high-load or high-RPM driving when oil is cold; allow warm-up before aggressive driving.
- Use quality fuel and address detonation or pre-ignition; ensure correct octane for your model and grade of fuel.
- If sludge risk is a concern for your model, schedule regular oil changes and follow Subaru guidance on oiling maintenance.
- Inspect wheels and tires; fix alignment issues and ensure proper wheel torque to prevent hub-related bearing wear.
These preventive measures help reduce both engine bearing wear and wheel bearing fatigue, extending the life of Subaru rotating components.
Diagnostics and when to seek service
Early signs that warrant inspection by a qualified technician include persistent metallic noises, vibration, or changes in oil pressure readings, as well as abnormal wheel noises or play in the wheel area.
- Engine: knocking or rumbling noise from the lower engine, especially at idle or under load; warning lights related to oil pressure or check engine.
- Driveline: grinding, growling, or rumbling from wheels or hub area; changes with speed or turning.
- Oil-related signs: sudden oil consumption increase, visible leaks, or dark metallic particles in oil samples.
- Inspection: unusual bearing play, abnormal heat in the bearing housings, or uneven wear on journals when inspected during rebuilds.
If you notice any of these symptoms, stop driving if safe and arrange diagnosis promptly to prevent catastrophic engine damage or wheel-related failure.
Model-specific notes and recalls
Subaru has run multiple recalls and service campaigns over the years related to oiling systems, oil pumps, and engine internals in various models and generations. Check Subaru’s official recall database or talk to a dealership about your vehicle’s VIN to confirm any open campaigns or recommended service actions that pertain to oiling or bearing-related issues.
Summary
Bearing failure in Subaru vehicles is largely a story of lubrication and wear. Engine bearings suffer when oil delivery, level, or cooling falter, while wheel bearings fail due to contamination, damage, or fatigue. Regular maintenance, prompt addressing of leaks or overheating, and careful driving habits are your best defenses, along with timely professional inspection if unusual noises or warning signals appear.
What is the most common cause of engine bearing failure?
What Are the Common Causes of Bearing Failure?
- Improper lubrication. Most failures happen as a result of improper bearing lubrication.
- Contamination and corrosion.
- Misalignment.
- Fatigue.
- Bearing selection and operational stress.
- Bearing mounting and installation.
How long should Subaru wheel bearings last?
Typically, there is no maintenance required for your Subaru wheel bearings, but a replacement is usually needed after 100,000 miles of driving.
Why do Subaru rod bearings fail?
Why Do Rod Bearings Commonly Fail on Subarus? Well… it all has to do with oil, the oiling system, and the general small surface area of Subaru rod bearing. Oil contamination or “dirty oil” causes little scratches or scoring on the bearings which impedes them from keeping a consistent oil film.
What is the most common cause of wheel bearing failure?
What causes a wheel bearing to become worn? Friction can never be truly eliminated, only reduced, and over time wheel bearings themselves wear out, though the most common reason for wheel bearings to fail is that their seals let the grease out, and water and grit in, damaging the balls and tapers.
