Vehicles using EJ255 engine list:

Engine EJ255

Symptoms:
- Oil consumption and leaks, especially from the valve cover gaskets and turbo oil lines.
- Head gasket failures leading to coolant leaks or overheating.
- Turbocharger issues such as boost leaks or reduced performance.
- Timing chain tensioner noise or failure causing rattling sounds.
- Carbon buildup on intake valves affecting engine smoothness and power.

Diagnosis:
- Inspect for oil leaks around valve covers, turbo oil feed and return lines.
- Perform a cooling system pressure test to detect head gasket leaks.
- Use a boost leak tester to check for turbo system integrity.
- Listen for unusual timing chain noise during cold starts.
- Conduct a compression test or leak-down test to assess head gasket and cylinder health.
- Use a borescope to inspect intake valves for carbon deposits.

Fixes:
- Replace valve cover gaskets and turbo oil lines if leaking.
- Repair or replace head gaskets; often requires engine removal and thorough cleaning.
- Service or replace the turbocharger if boost leaks or performance loss are confirmed.
- Replace timing chain tensioners and guides to eliminate noise and prevent chain skipping.
- Perform walnut shell blasting or professional intake cleaning to remove carbon buildup.
- Regular oil changes with high-quality synthetic oil to maintain engine health.

Prevention:
- Adhere strictly to recommended oil change intervals using Subaru-approved synthetic oils.
- Monitor coolant levels and maintain the cooling system to prevent overheating.
- Avoid prolonged idling and aggressive driving to reduce stress on the turbo and timing components.
- Use high-quality fuel to minimize carbon deposits.
- Regularly inspect and replace worn gaskets and seals before leaks develop.
- Schedule periodic professional intake cleaning to prevent carbon buildup.