The 4 Most Frequent Subaru EJ255 Engine Issues

The 4 Most Frequent Subaru EJ255 Engine Issues. EJ255 Subaru engines are 2.5L turbo flat four engines featured in a variety of US cars from 2004 to 2014. As of 2020, the engine is still in use in other parts of the world. It comes with a powerful engine that produces 210-265 horsepower. EJ255 engines are also widely renowned for being responsive to tuning and modifications. The EJ255 is an excellent overall engine. Unfortunately, no engine is perfect, and this is no exception. This post will go over some frequent Subaru EJ255 issues and reliability.

The 4 Most Frequent Subaru EJ255 Engine Issues

What Subarus Make Use of the EJ255?

The 2.5L EJ255 Subaru engine can be found in the following vehicles:

  • 2006-2014 Subaru Impreza (WRX)
  • Forester XT models from 2004 to 2013.
  • From 2005 to 2012, the Legacy GT
  • 2005-2009 Subaru Outback XT
  • From 2004 through 2006, the Baja Turbo

Certain non-US models still use Subaru EJ255 engines. The years and models listed above are for EJ255 variations sold in the United States. We may mention various models, such as the WRX, but it’s all in reference to the same 2.5L EJ255 engine. With that out of the way, let’s look at some of the most prevalent issues with the EJ255 motor.

Common Subaru EJ255 Issues

Among the most prevalent EJ255 concerns are:

  • Failure of the turbocharger
  • Ringland issues
  • Failure of the rod bearing

A few basic observations that will be expanded on later in this post. Even because these are referred to as typical concerns does not guarantee that they will affect the majority of vehicles. Also, the 2.5L EJ255s are getting old, thus a variety of other issues are possible. Oil leaks, cooling system issues, and other issues can and do occur on Subaru EJ255 engines.

We’ll go over the issues raised above in more detail later in this essay. It’s worth noting that when you adjust and modify the EJ255, some of these issues become more common. Keep that in mind if you want to add some bolt-on modifications to your Subaru. However, some issues may look more widespread on models such as the Impreza WRX, which is probable due to more Subaru WRXs being modded than Foresters, for example.

1) Subaru EJ255 Turbo Troubleshooting

With the EJ255 engine, there are several causes of turbo issues and failure. Before we get into the actual failures that have an underlying cause, let’s talk about aging. The majority of Subaru EJ255 engines on the road are about 10-15 years old. Turbos can endure the life of the vehicle, although they are subject to wear and strain. Random turbo failures are not unusual, especially at 150,000 miles or more. This could be stated about any turbo engine, not just Subaru’s. Going on to the actual issues that could lead to turbo failure.

The oil filters on EJ255 engines are extremely tiny. The microscopic filters become clogged with time, and engine oil begins to bypass the filter. Subaru EJ255 turbochargers get oil via a banjo bolt with a mesh screen. Unfiltered oil might cause tiny material to accumulate in the banjo bolt, reducing oil flow to the turbo. A turbo with little or no oil flow will not fare well. Upgrade to a larger oil filter, such as the OEM Mazda filter, which is a straight fit for the EJ255 engine. You should also think about replacing or cleaning the banjo bolt.

A turbo failure may cause internal engine damage in rare situations. This happens when the turbo sheds metal into the oil, which is picked up and pulled through the engine. Not to alarm anyone, but it’s another reason why maintaining the banjo bolt, oil filter, and oil is critical.

Signs of EJ255 Turbocharger Failure

With the Subaru EJ255, look for the following signs that may suggest turbo problems:

  • The smoke produced by exhaust
  • Increased turbo whine
  • Power decline
  • Boost is not reaching its target

Subaru EJ Turbo Upgrade

Turbo replacement on the Subaru EJ255 can be somewhat costly. Old turbos can be found for less than $1,000, however new OE turbos cost roughly $1,500. Labor costs might also mount up quickly if you aren’t doing it yourself. Changing the EJ255 turbo isn’t difficult, but it does require some time and patience. We recommend that turbo repairs be left to skilled do-it-yourselfers or those ready to spend a weekend in the garage.

2) Oil Leaks from the EJ255 Valve Cover Gasket

We’re not going to spend much time on this one. Because of any design problems in the EJ255, this isn’t a very prevalent issue. Rather, it is an example of a gasket that is prone to wear and tear. With age and mileage, valve cover gaskets (VCG) are prone to fail and leak oil. Because the Subaru EJ255 engine is a flat four, there are two valve covers and gaskets.

VCG oil leaks are frequently found north of 100,000 kilometers and 10 years old. Yet, they may begin to leak sooner. It’s not normally an emergency repair that needs to be done right away. Nonetheless, oil leaks should always be repaired as soon as possible.

Symptoms of Subaru EJ255 VCG Failure and Replacement

Signs of an oil leak in the 2.5L Subaru engine include:

  • Engine compartment smoke
  • Visible dripping
  • The odor of burning oil

Check the EJ255 valve cover locations if you observe smoke coming from the engine bay. A noticeable VCG leak will be a dead giveaway. If the oil is spilling onto hot areas, you may notice burning oil aromas.

The valve cover gaskets on a Subaru WRX EJ255 are simple to replace. The coil packs, breather hoses, and bolts that hold the valve cover in place must all be removed. It may take some time and patience for less experienced DIYers. Because EJ255 gaskets are quite inexpensive, this is not a major replacement. Going to a repair shop, on the other hand, could cost several hundred dollars in labor.

*A Quick Note Before We Go On

Issues with EJ255 ringlands, pistons, and rod bearings are more common in modified engines. These failures do occur on standard engines on occasion, especially as the engines age and mileage increases. Nonetheless, it is critical to recognize that altering your WRX EJ255 may increase the likelihood of these difficulties occurring. You can try to decrease the risks by using a good, conservative tune and the right supporting mods. Maintenance and oil changes also help to reduce the likelihood of these problems.

A suitable, conservative tune may potentially aid in the prevention of these disorders. Subaru modified the EJ255 and EJ257 engines to run slightly lean. This can lead to detonation problems and engine damage. Nevertheless, if you’re tuning for 350+whp, the risk is likely to balance out or increase.

3) Subaru EJ255 Ringland and Piston Issues

Nonetheless, the Subaru EJ255 has three piston rings. Upper and lower compression rings, as well as an oil ring, are present. The ringlands on the EJ255 are the areas between the three piston rings. Cracks on the ringlands are the most common cause of piston issues. On the ringland, a minor crack isn’t a big concern as long as it stays that way. It’s probably not even evident unless the engine is disassembled.

Unfortunately, those cracks may develop with time, resulting in the loss of a part of the piston, ring, or ringlands. When this occurs, the repercussions are severe. You will lose some, if not all, compression on the affected cylinder. It may also cause cylinder wall deterioration. The point is, this is a major problem that frequently necessitates the purchase of a new EJ255 engine. But, depending on the amount of the damage, it may be rebuildable.

Signs of EJ255 Ringland Failure

Among the possible signs of EJ255 ringland or piston failure are:

  • The engine is knocking or ticking.
  • Loss of compression
  • Power outage
  • The smoke produced by exhaust

If you lose a piece of the piston(s), the engine may make a ticking/knocking sound. This isn’t always the case, but it can happen if something is in contact with the cylinder wall. Because the piston will no longer adequately “close” the combustion chamber, compression in that cylinder will be lost. This will result in a loss of power. Furthermore, oil may pass between the rings, enter the combustion chambers, and cause the engine to smoke.

Replacement Ringland/Piston for Subaru EJ255

In the best-case scenario, the motor will need to be opened up to determine the extent of the damage. It may be rebuildable, requiring a new piston and the walls to be machined. If it cannot be rebuilt, you will require a new EJ255 engine. Repair costs will mount in either case, and this work should be left to professionals with extensive experience.

4) Failure of the Subaru EJ255 Rod Bearing

Another internal engine issue for the EJ255 that isn’t enjoyable to talk about or think about. Rod bearings are the components that link the connecting rods to the crankshaft. EJ255 rod bearings are subjected to a lot of abuse, and they’re usually the first to fail when there’s a problem with oil flow. Bearing failure is further increased by a lack of maintenance history and oil change intervals. The same may be true about increasing boost and power to the Subaru EJ255 engine.

When these bearings fail, the rods will often knock against the cylinder walls. You might potentially blow a hole in the engine block or cause the motor to seize. In any case, rod bearing difficulties and rod knock are highly serious issues. The EJ255 engine is unlikely to be rebuildable. Even if it is, the price of rebuilding will most certainly exceed the costs of finding a replacement motor.

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Bearing Replacement for EJ255

If found early enough, you may be able to get away with simply replacing the bearings. To ensure that the rod bearings did not cause too much damage to the crank surface, inspect the crankshaft for damage. Otherwise, it may need to be machined, or the entire motor may need to be replaced. Again, this task should be left to experienced mechanics and do-it-yourselfers who know what to look for.

EJ255 Subaru Reliability

How trustworthy is the Subaru EJ255 engine? We’re hesitant to call it a very reliable engine because some of the EJ255’s regular issues are serious and costly to repair. But, keep in mind that the internet has a tendency to exaggerate some things. With EJ255 engines, these problems and breakdowns can and do occur. Nonetheless, regular maintenance and oil changes can help prevent internal engine damage.

Treat your Subaru EJ255 well, and it will most likely reward you. If you are in the market, search for a well-kept example. Sometimes it’s just a matter of luck, but that applies to any model or automobile manufacturer. We don’t think the EJ255 is quite as horrible as some might have you believe. Yet, calling the EJ255 dependable may be a bit of a stretch. That’s not because it’s riddled with innumerable common issues. Rather, some of the difficulties may be really serious.

The 4 Most Frequent Subaru EJ255 Engine Issues

Summary of Subaru EJ255 Common Issues

The Subaru EJ255 is a good all-around engine. It has a remarkable performance from the 2.5L turbo flat four, which has its own distinct sound. The EJ255 also has a lot of information and aftermarket support. EJ255s respond well to mods as well, but they have limitations. Stick with a cautious tune or update the internals if you wish to modify your Subaru 2.5L.

The number of issues with the EJ255 does not alarm us. In that regard, it’s a dependable engine. Turbo failures and internal problems with rings, ringlands, pistons, and rod bearings, on the other hand, can be costly. Because the engines are aging, expect normal wear and tear items like valve cover gaskets, coolant hoses, and so on. But, if you take care of your EJ255, it will most likely reward you with an enjoyable, dependable experience.