Common Problems with the Subaru EJ25 Engine and How to Avoid Them When Buying
Common Problems with the Subaru EJ25 Engine and How to Avoid Them When Buying
Full Overview + Engine Specs | Quality EJ25 Engines for Sale
Introduction: Why the EJ25 is Such a Favorite—and What You Should Know Before You Buy
The Subaru EJ25 engine is arguably the most popular and ubiquitous engine of Subaru’s EJ line of engines. It has powered such legendary vehicles as the WRX, Forester, Legacy GT, and Outback, and the EJ25 has developed a cult following over the years because of its unique boxer configuration, balance, and tunability. Common Problems with the Subaru EJ25 Engine
But with popularity comes a touch of notoriety as well—particularly where long-term reliability and some of those mechanical flaws are concerned.
Whether you’re a mechanic looking for a project engine or simply want a reliable used EJ25 to replace a blown motor, knowing the common issues can save you thousands and provide you with a more educated buying choice.
Below, we’ll go over:
- The most common problems with the EJ25 engine
- How to prevent these problems if you’re purchasing
- Full engine details
- Why buying a quality-inspected Subaru EJ25 from a respected seller like us is your best option
What Is the Subaru EJ25 Engine? – Overview and Specifications
Before we proceed to the problems, here’s a quick summary of the EJ25 engine specs so you know what drives this engine.
EJ25 Engine Specifications:
| Specification | Details |
|---|---|
| Engine Code | EJ25 |
| Configuration | Flat-4 Boxer (Horizontally Opposed) |
| Displacement | 2.5L (2457 cc) |
| Valvetrain | SOHC / DOHC 16-valve |
| Fuel Type | Gasoline |
| Aspiration | Naturally Aspirated / Turbocharged |
| Bore x Stroke | 99.5 mm × 79 mm |
| Compression Ratio | 10.0:1 (NA) / 8.0:1–9.5:1 (Turbo) |
| Horsepower | 165–305 hp (model/year specific) |
| Torque | 166–290 lb-ft |
| Redline | ~6,500–7,000 RPM |
| Applications | WRX, WRX STI, Forester XT, Legacy GT, Outback, Impreza |
Depending on the vehicle model and model year, there are several different versions of the EJ25 engine (EJ251, EJ253, EJ255, EJ257, etc.). Turbo models like the EJ255 and EJ257 are performance Subarus.
Common Subaru EJ25 Engine Issues
The EJ25 is a great engine, but even it is not immune to its own set of common issues. It’s important to know what they are in order to make an informed purchase, whether it’s a used vehicle or a replacement engine.
1. Head Gasket Failure
The Issue:
Perhaps most well-known EJ25 engine issue. Older EJ25 model head gaskets (EJ251 and EJ253 models) leak outside (oil/coolant leaks) or inside (into the combustion chamber).
Why It Happens:
- Insufficient OEM gasket material
- Overheating
- Weak cooling system
- Poor maintenance
Prevention:
- When buying an EJ25 engine, ensure head gaskets have been replaced with newer multi-layer steel (MLS) types.
- Demand compression test or leak-down test records.
- Avoid engines with signs of overheating or milky oil (a sign of coolant mixing with the oil).
2. Ringland Failure (Especially on EJ255 / EJ257)
The Problem:
It usually happens mostly on turbocharged EJ25s. The “ringlands” on the pistons—the areas of the piston rings—can crack or break, causing loss of compression, misfire, or engine failure in a spectacular way.
Why It Happens:
- Aggressive tuning or modifications
- Low quality fuel
- Detonation/knock
How to Avoid It:
- Buy an engine from a stock, non-tuned car.
- Avoid engines with uncertain tune history.
- Choose low-mileage engines or remanufactured engines with forged pistons.
3. Rod Bearing Failure
The Problem:
Rod bearing failure creates knocking noises and ultimate engine seizure. It’s more common in abused engines or high-stress usage without proper oil maintenance.
Why It Happens:
- Low oil pressure
- Dirty or worn-out oil
- Severe driving without proper warm-up
How to Avoid It:
- Choose engines with documented oil changes.
- Check the oil pan or have it dropped at the inspection time (for metal shavings).
- Choose an engine from a reputable vendor who inspects internal components before resale.
4. Turbocharger Issues (EJ255 / EJ257)
The Problem:
Turbochargers can fail due to oil starvation, worn seals, or bearing wear. The outcome is low performance and oil consumption.
How to Avoid It:
- Choose an engine that has a good, original or rebuilt turbo.
- Look for play in the shaft or oil leaks.
- Ask the seller if the turbo was tested or replaced.
5. Failure of Timing Belt
The Problem:
Timing belts must be changed at 100,000 km (60,000 miles) or so. They will cause valve-to-piston contact, which destroys the engine, if they break.
How to Avoid It:
- Check if the timing belt has been replaced (ask for proof or invoice).
- Choose engines with new timing parts installed.
Tips for Buying a Good EJ25 Engine
Here’s how to protect yourself from buying a lemon and making sure your replacement engine will endure:
✅ Buy from a Reputable Supplier
Most important is to buy from a good seller who:
- Tests engines before shipping
- Offers warranties
- Is transparent about mileage, condition, and test results
- Offers installation support or technical advice
At our store, we provide guaranteed high-quality Subaru EJ25 engines inspected, cleaned, and compression-tested prior to sale.
✅ Choose the Right Version for Your Vehicle
There are several variants of EJ25, and they are not universal. Determine the right engine code that you need (e.g., EJ253 vs EJ255 vs EJ257).
We can help determine the right engine match on the basis of:
- VIN
- Transmission type
- ECU compatibility
- Emissions configuration (California vs Federal)
✅ Check or Ask for Test Results
When purchasing an EJ25 engine, always:
- Request compression/leak-down test results
- Check for oil leaks, cracked heads, or signs of overheating
- Ask for pictures or video of the engine running (if possible)
✅ Look for Rebuilt or Refreshed Engines
Low-mileage engines are wonderful, but rebuilt engines can be even better—especially if they’ve received:
- New head gaskets
- New timing components
- Forged internals (for use in a performance engine)
We sell remanufactured EJ25 engines with head gasket upgrade, seals, and performance upgrades for turbo installations.
✅ Warranty and Return Policy Check
A reputable engine seller will warrant (i.e., 30 to 90 days) their EJ25 engines and an equitable return policy.
We stand behind all of our engines with warranty coverage and technical support to aid in installation or compatibility issues.
Why Buy an EJ25 Engine from Us?
We’re not just some other parts store—our specialists are Subaru engine gurus who take the time to test, inspect, and prepare our EJ25 engines before they ever leave our facilities.
What We Offer:
- Equipped Subaru EJ25 engines for sale
- Compression leak-down tested
- New head gaskets and seals installed
- Low-mileage or rebuilt alternatives
- Warranty and support included
- Nationwide fast shipping
Whether you’re rebuilding a blown engine or beginning a new construction, we’ve got the right EJ25 engine for your car—and we’re here with you all the way.
Conclusion: Save Your Investment—Buy Smarter, Drive Prouder
The Subaru EJ25 is a good engine if properly serviced, but its typical faults render purchasing an old or replacement engine a bit challenging.
By knowing what to look for—and buying from an experienced, knowledgeable vendor like us—you can avoid costly mistakes and enjoy years of Subaru EJ25 driving pleasure.
If you’re truly interested in buying a good Subaru EJ25 engine, call us now. We have OEM used and rebuilt EJ25s available for high-performance applications and everyday driving. We’ll match you up correctly.
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✅ Get the right EJ25 for your Subaru
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