4 Most Common Subaru EJ25 Engine Problems

“STU TU TU!” which gearhead can forget this mesmerizing exhaust note of the iconic Subaru EJ25? Available both as turbocharged and naturally aspirated, this legendary engine can be found under the hoods of some of the most iconic Subaru models.

How legendary the Subaru EJ25 may be, it has its fair share of issues. In this article, we will tell you all about the most common issues with this power plant.

Overall, we can safely say that the reliability of the Subaru EJ25 is good compared to its peers. However, that doesn’t say this engine is a gift from heaven either. Failing turbochargers, rod bearing issues, coolant mixing with engine oil, and broken ringlands are some common problems EJ25 owners should look out for.

A Closer Look At The EJ25 Engine

The Subaru EJ25 is 2.5 liters in displacement, and its 4 cylinders are laid out in a “boxer” configuration. It comes equipped with either electronic fuel injection or sequential multi-point fuel injection. Some popular Subaru models powered by the EJ 25 include the WRX, Legacy, and Forester.

The EJ25 was preceded by the 120-horsepower EJ20 and the 135-horsepower EJ22 engines. Compared to its predecessors, the EJ25 was vastly powerful. Depending on the state of the tune, it could produce anywhere from 155 to 341 horsepower.

Since its introduction in 1996, the EJ25 underwent several design refreshes. The initial model was called the EJ25D. It was found under the hood of models like the Impreza 2.5 RS and the 1998 Forester.

Some key design features of the EJ25D were its Dual Overhead Cam (DOHC) architecture and the offset crankshaft design.

Subaru released the next version of the EJ25 engine around the turn of the millennium. Named the EJ251, it powered models like the Legacy, Outback, Baja, Impreza, and Forester models were made from 2000 to 2005.

Subaru also produced an alternate version of this engine to meet California emissions standards. Unsurprisingly, they named it the EJ252. The 2000 – 2001 Legacy Outback was the only vehicle to come with this engine.

The EJ252 came with a drive-by-wire throttle system. Additionally, the cylinder liners were made thinner and lighter.

Around 2004, a more performance-oriented version named the EJ255 made its debut. 2019 saw the introduction of the EJ257, which has a revised block design, W25 cylinder heads, and a new crankshaft design.

Subaru EJ25 Engine Problems

Thanks in part to its rugged construction, most EJ25-powered Subarus remain on public roads to this day. However, there are some issues commonly associated with this engine.

If you own a vehicle powered by the Subaru EJ25, here are some engine problems to keep an eye out for;

  • Rod Bearing Issues
  • Broken Ringlands
  • Coolant Mixing With Oil
  • Damaged Turbocharger

Now, let’s take a closer look at each of these issues. We’ll tell you the causes behind them, as well as the most common symptoms.

1. Rod Bearing Issues

Rod bearings are responsible for connecting the crankshaft of the EJ25 to the connecting rods. So, there will be some serious consequences when this part goes bad.

Loss of engine oil pressure during cold startups, rod knock in high RPMs, and metal shavings in engine oil are some early indications of rod bearing failure.

Several causes can result in rod-bearing failure. Inadequate engine lubrication is one of the most common ones. Sudden loss of oil flow or pressure during high RPMs causes the rod bearing to spin and get damaged, ultimately leading to failures.

The rod bearings may fail due to natural wear and tear as well. The choice of material has a significant effect on the lifespan of rod bearings. For example, bi-metal rod bearings will wear out noticeably faster when compared to ones made of tri-metal.

Excessive heat is another catalyst for rod-bearing failure. Heat wears out the protective film layer on the bearing, leading to metal-on-metal contact. The constant friction generates more heat, ultimately resulting in catastrophic consequences.

2. Broken Ringlands

Thick smoke oozing out of the exhaust, loss of engine compression, power loss, and clunking noises coming from the engine is some symptoms of EJ25 ringland failure. But, what exactly is a ringland?

You see, the Subaru EJ25 comes with three piston rings. The areas between each of these pistons are called ringlands. Over time, cracks may begin to form in this area.

Although minor ringland cracks are nothing to worry about, it is still important to keep an eye on them. These cracks can spread, resulting in severe consequences. We are talking about ringland cracks, or even piston failures.

Piston cracks severely damage the cylinder walls. Not only that, but the engine will completely lose compression too.

Once again, Several causes may end up resulting in EJ25 ringland failure. Filling up the vehicle with low Octane fuel is one major cause. Fuel with low octane levels burns faster, putting enormous stress on the engine internals. This wear and tear can add up and destroy the ringlands.

Wrong engine tunes can lead to ringland failure as well. All components of the engine should be in perfect harmony for it to work properly. If this doesn’t happen, the pistons won’t run smoothly. Thus, leading to failures.

3. Coolant Mixing With Oil

Engine oil and coolant are two things that should never get together inside an engine. Coolant hampers the oil’s ability to lubricate engine internals. Lack of lubrication leads to a host of engine issues such as piston ring failure and crankshaft problems.

Sadly, this is another common issue with the EJ25 engine. The formation of coolant puddles under the vehicle, a sweet smell coming from the exhaust, and milky residue on the crankshaft are some tell-tale signs.

Usually, the presence of coolant in engine oil is the result of a much more severe engine problem. A damaged head gasket is one possible cause, and cylinder head cracks are another. Additionally, faulty oil coolers and cracks in the engine block can also cause the two liquids to cross paths.

As you can understand, you shouldn’t take the mixing of coolant and engine oil lightly. It has the potential to cause complete engine failure. If you are experiencing any of these symptoms, make sure to book an appointment with your local Subaru dealership as soon as possible.

4. Damaged Turbocharger

Just like we told you earlier, some versions of the EJ25 came equipped with a turbocharger for additional performance. But, this additional performance came at the cost of some reliability problems.

Engine power loss, loud turbo whine, excess smoke coming from the exhaust, and lower boost levels are some common symptoms of EJ25 turbocharger failure.

Turbocharger failure usually sets in once the vehicle has passed the 150,000-mile mark. Clogged oil filters are the main reason behind turbo failure. On some occasions, metal shavings from the failed turbo may enter the engine and damage the internals as well.

Replacing the turbocharger on the Subaru EJ25 is fairly expensive. Although the replacement job is not that complex, it should be attempted with some patience. A used turbocharger for this engine costs about $1000, while a brand-new one will run you around $1500.

Preventive Maintenance Tips To Keep The EJ25 Running Smoothly

Most of the aforementioned engine issues with the EJ25 often cost hundreds of dollars to fix. So, we thought of giving you some tips that can hopefully prevent them from happening.

Get A Bigger Oil Filter

Most EJ25 turbo failures are caused due to clogged oil filters. These engines came from a smaller oil filter from the factory, that got clogged in the blink of an eye.

One of the best ways of preventing turbo failures is by replacing the factory oil filter with a larger aftermarket one. OEM Mazda oil filters are one of the best direct replacements.

And while you’re at it, consider swapping out the banjo bolt as well. If it’s still in operating condition, give it a good cleaning for better reliability.

Use Fuel Of the Correct Octane Level

As we mentioned, using lower than Octane gas is disastrous for your engine’s pistons and ringlands. So, make sure to fill up your gas tank only with the manufacturer-recommended Octane level fuel.

Follow Proper Maintenance Procedures

Changing engine oil at the correct intervals and adhering to the maintenance schedule are important for the longevity of any engine. When it comes to the Subaru EJ25, doing so will prevent the rod bearings from going bad.

Get A Proper Engine Tune

The EJ25 comes from the factory with a tune that makes it run on a lean fuel/air mixture. As the engine ages, this can result in engine damage. Consider getting an aftermarket tune, especially if you are planning to add performance modifications down the line.

If you are the proud owner of a Subaru with an EJ25 engine or planning to purchase one in the future, make sure to be prepared for these problems. Also, remember to make use of the tips that we provided to limit engine problems in the first place.

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Mahir Ahmed


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