Comprehensive DIY Guide to Cleaning a Subaru EJ205 Engine Cylinder Head

Understanding the Subaru EJ205 Engine

The Subaru EJ205 is a turbocharged 2.0L horizontally opposed (boxer) four-cylinder engine manufactured between 1999 and 2014. This versatile, high-performance engine was used in a variety of Subaru models over the years, most notably the Japanese and European market Impreza WRX and WRX STI high-performance cars.

The EJ205 enjoyed great popularity among enthusiasts and developed a cult-like following due to its impressive factory power output combined with immense tuning potential. With the right modifications, EJ205 engines have been tuned to produce over 500 horsepower.

Why Cleaning the Cylinder Head is Important

Over time, carbon deposits, sludge, and contaminants can build up in the EJ205 cylinder head. This can restrict airflow reducing engine performance. Cleaning the cylinder head removes these deposits and helps restore optimal airflow and engine performance.

Cleaning the head also allows you to inspect the head gasket sealing surface for any warpage or imperfections that could cause future gasket failures and compression/coolant leaks.

Tools and Supplies Needed

Cleaning an EJ205 cylinder head can be done with some basic tools and supplies like:

• Safety glasses and gloves
• Spray gasket remover or paint stripper
• Razor blades/gasket scrapers
• Assorted wire brushes
• Shop towels or rags
• Bucket and cleaning solvent (brake/carburetor cleaner)
• Compressed air source

Dissasembling Components from the Cylinder Head

Before cleaning, double check that all sensors, fuel injectors, camshafts, rocker arms, valves, valve springs and retainers have been removed. This allows unobstructed access for cleaning.

Spray any stubborn gasket remnants with gasket remover and let it penetrate for 5-10 minutes. Then carefully scrape away remnants with razor blades or gasket scrapers. Take care not to gouge the head's sealing surface.

Cleaning Process Step-by-Step

Here is the complete DIY process for cleaning an EJ205 Subaru cylinder head:

1. Fill bucket with cleaning solvent. Dip coarse wire brush and scrub cylinder head exterior to remove thick oily grime and deposits. Rinse brush frequently in solvent.

2. Pour solvent into the head's ports and combustion chambers. Let it soak for 10 minutes to soften carbon deposits. Use spray solvent to assist in tight areas around valves/seats.

3. Use assorted bottle brushes pushed by hand or low speed drill to scrub cylinder head ports and combustion chambers. Remove heavy carbon deposits and sweep away sludge.

4. Use compressed air to thoroughly dry head's passages, ports and chambers. Spray more solvent and hand brush to catch leftover residue loosened by the air.

5. Inspect head sealing surface for any warpage or damage. Resurface via milling machine if out of spec. Also check valve seats for wear or recession.

6. Use razor blade to gently scrape any last carbon specks or paint remnants from head surface without gouging metal. Wipe surface clean with solvent dampened rag.

7. Blow out all passages with air again. Place head on clean towel and give one last visual inspection while wearing bright light. Repeat previous steps if any noticeable grime remains.

Remaining Steps to Reassembly

After cleaning is complete, reinstall your cylinder head valves, springs, rocker arms, cam shafts and all other components correctly before placing back on the Subaru EJ205 short block.

Be sure to use a new Subaru OEM cylinder head gasket for reliable sealing without any future compression or coolant leaks.

Following the proper EJ205 cylinder head cleaning techniques when rebuilding your high mileage WRX or STI engine will help ensure optimal airflow, power gains and reliable performance for years to come.

FAQs

How often should I clean the cylinder head?

For high performance Subaru engines like the EJ205, it's a good idea to clean the cylinder heads every 60,000-100,000 miles when doing a rebuild or major service. This helps remove carbon deposits and maintain optimal airflow.

What causes carbon buildup in the heads?

Carbon deposits and sludge form over time from blow-by gases, fuel residue and contaminants in the intake air. This buildup gets worse if the PCV system isn't working properly or if the engine has been modified to run rich.

Will cleaning the heads give me more power?

Yes, removing built up carbon opens up the airflow pathways. This allows your EJ205 to breathe and rev more freely, increasing horsepower, throttle response and engine efficiency.

Can I just use carburetor cleaner to clean the heads?

You need a heavy duty solvent like brake parts cleaner or dedicated head/block cleaner. Carb cleaner can work for light cleaning jobs but often lacks the cleaning strength needed to remove heavy carbon on high performance engines.