Vehicles using EJ204 engine list:

Engine EJ204

Symptoms:
- Excessive oil consumption
- Head gasket failure leading to coolant leaks or overheating
- Timing belt wear or failure causing engine misfires or no-start conditions
- Rough idling or loss of power due to carbon buildup
- Check Engine Light (CEL) illumination with related fault codes

Diagnosis:
- Inspect oil level and quality regularly; look for blue smoke or oil residue
- Perform a cooling system pressure test to detect head gasket leaks
- Check timing belt condition and tension; inspect for cracks or wear
- Use a diagnostic scanner to read fault codes related to misfires or sensor failures
- Conduct a compression test to assess cylinder health and gasket integrity

Fixes:
- Replace worn or leaking head gaskets promptly to prevent engine damage
- Change timing belt and associated components (tensioner, pulleys) at recommended intervals (typically every 100,000 km or 60,000 miles)
- Address oil consumption by replacing valve stem seals or piston rings if necessary
- Clean or replace intake valves and throttle body to reduce carbon buildup
- Repair or replace faulty sensors triggering CEL, such as oxygen sensors or MAF sensors

Prevention:
- Adhere strictly to scheduled maintenance, including oil changes with high-quality synthetic oil
- Use coolant with proper specifications and maintain correct coolant levels
- Replace timing belt and tensioner components proactively before failure
- Avoid prolonged idling and aggressive driving to reduce engine stress
- Regularly inspect and maintain the cooling system to prevent overheating and gasket failure

Following these guidelines will help maintain the reliability and performance of the EJ204 engine in the specified Subaru Legacy and Outback models.