Subaru EJ255 Engine
Subaru EJ255 engines are 2.5L turbocharged flat four-cylinder engines found in a variety of 2004–2014 US models. As of 2020, the engine is still in use in other parts of the world.
It comes equipped with a powerful engine that produces 210-265 horsepower. Additionally, EJ255 engines are well-known for their responsiveness to tuning and modification.
The EJ255 is an extremely reliable engine in general. However, no engine is perfect, and this is not one of them. This guide discusses several common Subaru EJ255 problems and the vehicle’s overall reliability.
What Subaru’s Use the EJ255?
Subaru’s 2.5L EJ255 engine is used in the following vehicles:
- 2006-2014 Impreza (WRX)
- 2004-2013 Forester XT
- 2005-2012 Legacy GT
- 2005-2009 Outback XT
- 2004-2006 Baja Turbo
Subaru EJ255 engines are still used in some models sold outside the United States. The preceding table details the years and models of the EJ255’s US variants. While we may make specific model references throughout, such as the WRX, it is all in reference to the same 2.5L EJ255 engine. With that out of the way, let’s look at some of the more common issues with the EJ255 motor.
Subaru EJ255 Common Problems
Several of the most frequently encountered EJ255 issues include the following:
- Turbo failure
- Ringland problems
- Rod bearing failure
A few brief observations that will be expanded upon later in this article. Simply because we’re referring to these as common problems does not mean they affect the majority of vehicles. Additionally, the 2.5L EJ255 engines are aging, which means that a variety of other issues are possible. On Subaru EJ255 engines, oil leaks, cooling system problems, and other issues can and do occur.
We’ll discuss the aforementioned issues in greater detail throughout the remainder of this post. It’s critical to keep in mind that some of these issues become more prevalent as you tune and modify the EJ255.
Bear this in mind if you intend to add some bolt-on modifications to your Subaru. Having said that, certain issues may be more prevalent on models such as the Impreza WRX. Much of that can be attributed to the fact that more Subaru WRXs are modified than Foresters, for example.
1) Subaru EJ255 Turbo Failure
On the EJ255 engine, there are a few possible causes of turbo problems and failure. Before we get into the specific failures that have a root cause, let’s discuss age. The majority of Subaru EJ255 engines on the road today are between 10-15 years old. While turbochargers can last the lifetime of a vehicle, they are a wear and tear component.
Random turbo failures are not uncommon, especially at 150,000 miles or more. This is true of any turbocharged engine, not just these Subarus. Moving on to the actual issues that could result in turbo failure.
Oil filters on EJ255 engines are extremely small. The tiny filters clog up over time, and engine oil begins bypassing the filter. Subaru EJ255 turbochargers receive oil via a banjo bolt fitted with a mesh screen.
Unfiltered oil may deposit small particles in the banjo bolt, reducing oil flow to the turbo. A turbocharger with little or no oil flow will not perform well. Upgrade to a larger oil filter, such as the OEM Mazda filter, which is a direct fit for the EJ255 engine. Additionally, you may wish to replace or clean the banjo bolt.
In extremely rare instances, a turbo failure can result in internal engine damage. This occurs when the turbo discharges metal particles into the oil, which can be picked up and drawn through the engine. Not to scare anyone, but this is another reason why maintaining the banjo bolt, oil filter, and oil is critical.
EJ255 Turbocharger Failure Symptoms
Keep an eye out for the following symptoms on the Subaru EJ255 that may indicate turbo problems:
- Smoke from exhaust
- Louder turbo whine
- Loss of power
- Boost not reaching target
Smoke coming from the exhaust may indicate a turbo problem. However, this could also be a symptom of another issue. A sudden increase in turbo whine is usually a dead giveaway that your 2.5L EJ255 turbo is having issues. Additionally, you’ll likely notice a loss of power as a result of the turbo failing to provide enough boost.
Subaru EJ Turbo Replacement
Replacement of the turbocharger on the Subaru EJ255 can be quite costly. Used turbos are available for less than $1,000, while new OE turbos cost around $1,500. Labor costs can also add up significantly if you are not a do-it-yourselfer.
While replacing the EJ255 turbo is not difficult, it does require some time and patience. We recommend that experienced do-it-yourselfers or those willing to spend a weekend in the garage handle turbo repairs.
2) EJ255 Valve Cover Gasket Oil Leaks
We’re not going to spend a lot of time on this one. This is not a very common occurrence as a result of any design flaws in the EJ255. Rather than that, it is an excellent example of a gasket that is prone to wear and tear.
With age and mileage, valve cover gaskets (VCG) are known to degrade and begin leaking oil. Due to the fact that the Subaru EJ255 engine is a flat four, there are two valve covers and gaskets.
VCG oil leaks typically occur between 100,000 and 100,000 miles and are 10 years old. They may, however, begin leaking sooner. Typically, this is not an emergency repair that requires immediate attention. Oil leaks, on the other hand, should always be addressed promptly.
Subaru EJ255 VCG Symptoms & Replacement
Symptoms of a 2.5L Subaru engine that is leaking oil include the following:
- Smoke from engine bay
- Visible leak
- Burning oil smells
If you notice smoke emanating from the engine bay, inspect the EJ255 valve cover areas. A visible VCG leak is a dead giveaway. Otherwise, you may smell burning oil if the oil drips onto hot components.
The valve cover gasket replacement procedure for the Subaru WRX EJ255 is fairly straightforward. Remove the coil packs, breather hoses, and bolts that secure the valve cover. It may take some time and patience for less skilled do-it-yourselfers.
Because the EJ255 gaskets are relatively inexpensive, this is not a significant replacement. Although going to a repair shop may add a few hundred dollars to the labor cost.
*A Quick Note Before The Next Topics
Issues with EJ255 ringlands, pistons, and rod bearings are typically more prevalent on modified engines. These failures do occur on stock engines on occasion, especially as the engine ages and mileage increases. However, it’s critical to understand that modding your WRX EJ255 may increase your risk of encountering these issues.
You can attempt to mitigate the risks by using a high-quality, conservative tune and appropriate supporting mods. Maintenance and oil changes also contribute significantly to reducing the risk of these failures.
A conservative tune may even help avoid these problems. Subaru engineered the EJ255 and EJ257 to run slightly lean. This can result in detonation problems and subsequent engine damage. However, if you tune for 350+whp, the risk likely equalizes or increases.
3) Subaru EJ255 Ringland & Piston Problems
Having said that, the Subaru EJ255 features three piston rings. There are two compression rings, one upper and one lower, as well as an oil ring. The ringlands on the EJ255 are the areas between the three piston rings.
Typically, piston problems begin with cracks in the ringlands. Minor cracks are not a big deal on the ringland as long as they remain minor. It’s probably not noticeable at all – unless the engine is disassembled.
However, those cracks may expand over time, resulting in the loss of a chunk of the piston, ring, or ringlands. When this occurs, the repercussions are quite severe. You will lose some, if not all, compression on the affected cylinder.
Additionally, it may cause damage to the cylinder walls. To summarize, this is a fairly serious issue that frequently necessitates the purchase of a new EJ255 engine. However, depending on the extent of the damage, it may be rebuildable.
EJ255 Ringland Failure Symptoms
Several possible symptoms of EJ255 ringland or piston failure include the following:
- Engine knocking / ticking
- Compression loss
- Power loss
- Smoke from exhaust
If you lose a section of the piston(s), you may hear the engine ticking/knocking. This is not always the case, but it can occur if anything comes into contact with the cylinder wall.
Because the piston is no longer properly “sealing” the combustion chamber, compression in that cylinder will be lost. This will result in a loss of power. Additionally, oil can blow through the rings and into the combustion chambers, causing the engine to smoke.
Subaru EJ255 Ringland/Piston Replacement
In the best-case scenario, the motor will need to be opened to determine the extent of the damage. It may be rebuildable, but this would require a new piston and machining of the walls.
If it is not rebuildable, you will require a new EJ255 engine. In either case, the repair costs will accumulate, and this work should be left to highly experienced professionals.
4) Subaru EJ255 Rod Bearing Failure
Another internal engine issue with the EJ255 that isn’t particularly enjoyable to discuss or consider. Rod bearings serve as the mechanical link between the connecting rods and the crankshaft.
EJ255 rod bearings take a lot of abuse and are frequently the first to fail if there is a problem with oil flow. Bearing failure is also increased by a poor maintenance history and oil change intervals. Likewise, more boost and power can be applied to the Subaru EJ255 engine.
When these bearings fail, the rods typically knock against the cylinder walls. You risk blowing a hole in the engine block or seizing the motor. Rod bearing problems and rod knock are extremely serious issues regardless of how you look at it.
The EJ255 engine is unlikely to be rebuildable. Even if it is, rebuilding the engine will almost certainly cost more than finding a replacement motor.
EJ255 WRX Rod Bearing Failure Symptoms
Keep an eye out for the following rod bearing symptoms:
- Rod knock
- Metal shavings in oil
- Loss of oil pressure
Rod knock is a fairly disturbing sound that generally gets louder as the RPMs increase. The EJ255 is unlikely to sound particularly healthy. Bearing wear can be detected and corrected before it results in catastrophic failure.
Check for metal shavings in the oil or send it in for analysis on a regular basis. Additionally, you may notice a decrease in oil pressure, particularly during cold starts. If caught early enough, you may be able to save your engine from total destruction.
EJ255 Bearing Replacement
If caught quickly enough, you may be able to simply replace the bearings. The crankshaft should be inspected for damage to ensure that the rod bearings did not damage the crank surface excessively.
Otherwise, it may require milling or it may be more cost effective to replace the entire motor. Again, this work should be left to experienced mechanics and do-it-yourselfers who understand what to look for.
Subaru EJ255 Reliability
Thus, how trustworthy is the Subaru EJ255 engine? We’re hesitant to call it a very reliable engine due to the fact that a few of the EJ255’s most common issues are quite serious and require expensive repairs.
However, it’s critical to keep in mind the internet’s proclivity for exaggerating certain events. These issues and failures are possible on EJ255 engines and do occur. However, regular maintenance and oil changes help prevent internal engine damage.
Take good care of your Subaru EJ255, and it will likely reward you. If you’re in the market, look for an example that has been well maintained. At times, it’s a matter of luck, but that applies to any model or car brand.
We believe that the EJ255 is not nearly as bad as some would have you believe. However, labeling the EJ255 as reliable may be a stretch. That is not because it is beset by an infinite number of common problems. Rather than that, a few of the issues can be quite serious.
Subaru EJ255 Common Problems Summary
The Subaru EJ255 is a reliable engine in general. It boasts impressive performance thanks to the 2.5L turbo flat four engine, which emits its own distinct sound.
Additionally, there is a wealth of information and aftermarket support available for the EJ255. EJ255’s also respond well to modifications, but they have limitations. If you’re going to modify your Subaru 2.5L, opt for a conservative tune or internal upgrades.
We do not believe that the EJ255’s problem count is alarming. In that regard, it is a dependable engine. Turbo failures, on the other hand, can be costly, as can internal problems with rings, ringlands, pistons, and rod bearings.
Additionally, the engines are aging, so expect normal wear and tear items such as valve cover gaskets, coolant hoses, and so on. Nonetheless, maintain your EJ255 properly and you’re likely to have a pleasurable, reliable experience.
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