Subaru EJ25 Engine Problems: Is The Engine Reliable?

Learn why your Subaru EJ25 engine is bad

Not many over 15 years engine would still be available on the road today, but thanks to the ruggedness and strength of the Subaru EJ25 engine, which as at last year was still in use in different parts of the world. Despite its strength, certain problems are found with this engine.

The most common problems with the Subaru EJ25 engine include:

  1. Ringland/Piston Problems
  2. Oil-Coolant Mixture
  3. Rod Bearing problem

Different engines have different problems. However, these problems do not mean the strength and ruggedness of the engine are questionable.

The healthy and extended lifespan of the engine depends largely on the level of maintenance and attention you give to the engine.

What Are The Most Common Subaru EJ25 Engine Issues?

1. Ringland/Piston Problems

Subaru EJ25 is manufactured with three piston rings. They include the upper and lower, compression, and oil ring.

The engine begins to develop problems once there is a crack in the ringlands. The good thing about cracks on the ringlands is that minor cracks don’t pose a threat, in as much it doesn’t become wider.

Sometimes, you may even find it difficult to notice the ringlands have cracked, except the engine needs thorough inspection or repair.

Cracks may grow bigger over time as the engine continues to work. And when this happens, you end up losing chunks of the piston, ringlands, or rings.

Loss of chunks on any of these three components may require you to spend heavily as this may get rid of all or some of the compression on the cylinder.

It is possible it also spoils the engine’s cylinder walls. The result of this engine damage due to faulty ringlands and compression wall may mean you will need to save up for a new Subaru EJ25 engine.

However, if the level of damage isn’t too severe, you may need a rebuild.

What Causes Ringland problem

1. Low Octane Fuel

Low octane fuel can destroy the ringlands of your car. Generally, low octane fuel reinforces detonation which damages your engine.

The best thing to do is to switch to fuel of a higher octane number. This will ensure complete combustion and leave no carbon deposit in any part of the engine.

2. Lack of Proper Tuning

Components such as exhaust manifolds, downpipes and intakes require proper adjustments and tuning to meet the factory setting.

However, if the adjustments are not carried out properly, the pistons ring lands will not work smoothly.

Prolonged hard driving: Also called abusive driving, prolonged hard-driving increases the thermal load on your vehicle and ultimately invites detonation. Avoid driving for a long time.

What Symptoms To Look Out For

Since we already know that larger cracks in the Subaru EJ25 engine can wreck it if not taken care of, let’s take a look at the symptoms to note to avoid blowing things out of proportion.

  • Clucking Noise From The Engine: A tickling sound comes from this engine if there is a loss of chunk in the piston. Additionally, if there is contact between the cylinder wall and anything, it may result in a tickling sound from the engine.
  • Exhaust Smoke: Oozing smoke from the exhaust may indicate you have to pay attention to your Subaru EJ25 engine’s ringlands. Oil may blow by the rings and find its way into the combustion chambers. When this happens, it causes the exhaust to produce smoke.
  • Compression Loss: Subaru EJ25 engine loses compression once there is contact between the cylinder wall, causing the piston to not seal the combustion in the right way. With improper combustion chamber sealing, there will be a loss of compression in the cylinder.

What Fix To Apply

Fixing ringland problems in Subaru EJ25 requires opening up the motor to meet damage levels. There are two ways to fix this problem.

If the level of damage isn’t too high, you may rebuild the engine by buying a piston and the wall may need to be machined as well.

If the level of damage is high beyond rebuilding, you should consider a new engine. Whatever choice you are making between rebuilding and buying a new one, it is pertinent to know that both can be very expensive and should be handled by professionals with years of experience.

2. Oil-Coolant Mixture

Oil in the coolant is not only a common Subaru FA20 problem but also common with other engines too.

Subaru EJ25 gaskets were badly made that oil and coolant mixture with each other easily, hence, resulting in problems inside the engine. The mixture of oil and coolant will not let both oil and coolant do their job properly.

We shouldn’t forget that oil in engines helps to lubricate, while coolant helps to cool down the engine.

A mixture of both will prevent the oil from lubricating the engine properly. This will lead to inadequate lubrication, which will cause the engine parts to start wearing prematurely.

Take, for instance, insufficient lubrication will cause the failure of piston rings. The camshaft can begin to wear off. Problems with these two components will create more problems for the engine.

If there is also oil in the coolant, it will affect the coolant’s performance and will cause the engine to run at an extremely high temperature, leading to overheating. Oil in the coolant is a common problem in many Subaru models.

What Causes Oil-Coolant Mixture Problem

1. Damaged Head Gaskets

The rubber seal located between the engine block and cylinder head helps to seal oil from escaping from the engine. It also maintains the air pressure level.

Once it breaks, the head gasket will cause oil to leak into the coolant reservoir, causing the engine oil to leak way into the coolant system.

2. Cracks In The Cylinder Heads

Due to overheating, the cylinder head can break. The heads are not designed to hold out against extreme heat. Once the heads crack, the oil can easily leak out and drop in the coolant area.

3. Faulty Oil Cooler

Your Subaru EJ25 engine comes with a cooler fitter that can crack due to age or overuse. The oil can leak into the coolant reservoir when this crack happens.

4. Cracks In Engine Blocks

The engine block can also crack due to lack of oil and lubrication. If this happens, you’ll need a replacement.

Otherwise, the oil will continue to find its way into the coolant system, therefore contaminating the coolant and destroying the engine.

What Symptoms To Look Out For

I do not want us to blow things out of proportion without knowing the symptoms to watch out for if your Subaru EJ25 has got oil in the coolant problem.

  • Coolant Loss: A continual antifreeze drop in your Subaru EJ25 engine may indicate a mixture of coolants with oil, especially if there are no visible leaks, and the chances are high that the oil is finding its way into the crankcase.
  • Sweet Smell: Coolant leaking without a drop or visible on the engine bay may indicate oil has missed its channel to the oil pan. The mixture of oil and coolant produces a sweet smell, even if it is a few drops of oil in the coolant.
  • Milky Color: The crankcase is left with colors such as red, orange, green, or even brown as a result of coolant getting into the oil pan. Over time, as the engine works, there will be a mixture of oil and coolant, producing a milky liquid gumming up the engine’s passageway.

What Fix To Apply

Overall, the method to solve the above problem I have highlighted is straightforward but expensive.

You should consult a professional mechanic to help you check for likely causes of oil in coolant such as leaky head gaskets, overheating, or other likely causes.

3. Rod Bearing Problem

In automotive mechanics, issues with faulty or worn rod bearing shouldn’t be something to take with reckless flippancy.

The damage could portend serious danger to the overall performance of your vehicle. A rod bearing is a two-piece band of metal that helps to keep spinning shafts in place.

The smooth metal comes with a semi-circle top half that’s mounted to the wheeled frame beneath the vehicle. The rod bearing’s bottom half is bolted to the other half after spinning the driveshaft in place.

Typically, lubricant reaches the inside of the rod bearing through the pinhole and the shaft can spin freely without giving off much heat.

Since there are different bearings in the engine, it’s important to be sure which of the bearings is under attack. This way, you’ll be applying the correct remedy.

Essentially, connecting rods in the Subaru EJ25 engine is connected by rod bearings to the crankshaft. Due to the abuse of the connecting rod bearing, it is the first component to give oil flow problems.

Other causes of rod bearing failure are traceable to oil change intervals and poor maintenance.

When bearings wear out, they make connecting rods hit against the cylinder walls, and regardless of how minimal this can be, the problem is a very serious one.

The chances of not being able to rebuild this engine are, however, high and if it is rebuildable, the cost may exceed replacing a motor.

What Causes Rod Bearing’s Problem

1. Loss Of Lubrication

A sudden loss of oil flow, lubrication, and oil pressure between the journal and bearing can cause the rod bearing to spin.

When this happens, especially at high revolution per minute, the protective film will thin out and instantly disappear, leading to the crank being impeded from smoothly gliding.

2. Excessive Heat

Once the protective film disappears, you will notice metal-to-metal contact between the surfaces of the journal and the bearing.

This causes scuffing and reinforces the shaft to generate excess heat and friction in the process.

The metal will liquefy at very temperature (about 232oC), forming a sludge while holding firmly to the crank journal.

3. Failure Due To Fatigue

There are a lot of areas to look at when laying the blame for rob bearing wear on fatigue. When you choose the wrong material for the engine bearing, the bearing will wear out faster than normal.

For instance, if you select a bi-metal over tri-metal material, your car’s rod bearing will fail and wear in no time.

What Symptoms To Look Out For

  • Oil Pressure Loss: When you have a cold start of the engine, you will notice a loss of oil pressure. it sometimes indicates you have a failing rod bearing. You may be saving your Subaru EJ25 engine from complete ruin if you quickly pay attention to this symptom.
  • Rod Knock: As the engine’s RPM increases, the rod knock’s sound increases causing the engine not to produce a healthy sound.

What Fix To Apply

Fixing or replacing the rod bearing is the best way to solve the above problem I have explained. Although you may need to cough some bucks (in the range of $500 to $3000), it is worth the cost.

You may, however, be able to prevent the wearing of the rod bearing before leading to a catastrophic outcome if you regularly inspect your oil by checking for metal shavings. Early discovery of these symptoms may only require bearing replacement.

One of the first preventive steps is to select the correct engine bearing material with the required load capacity. Tri-metal material will be preferable to bi-metal.

Fuel detonation or advanced ignition can be remedied by using fuel with a higher octane value or retarding the ignition.

If the problem is linked to running the Subaru EJ25 engine at low RPM and high torque for long, the solution is to replace the engine bearing material with a more suitable and stable one.

You should inspect the bearing crash height or resize the casing if you notice that the bearing doesn’t conform back properly with the housing.

In the case of oil starvation that often causes over-concentration of load at particular bearing areas, you should inspect the oil supply system.

The oil passages may have been clogged; also oil pressure and volume, component geometry, and clearances. Geometric irregularities are a significant cause of the problem.

Otherwise, you may need to machine or replace the motor entirely. Replacing the entire engine may cost a huge amount while bearing replacement can go for a cheaper amount.

You should, however, employ the services of a good mechanic and if you are fixing this problem as a DIY, ensure you have detailed knowledge to prevent further damage to the engine.


1. What Are The Specifications Of The Subaru EJ25 Engines?

Features: Specs:
Displacement 2457 cc (338.8 cu in)
Turbocharger Naturally Aspirated
Fuel Type Gasoline
Piston stroke, mm (inch) 79 (3.62)
Configuration Flat-4
Valvetrain SOHC (2 valves per cylinder) and DOHC (4 valves per cylinder)

2. Is Coolant-Oil Mixture Dangerous?

Yes, it is. As I’ve pointed out and this is a no brainer, really, having the engine oil mixed with the coolant is terrible not only for the overall performance of your car but also for the health of your engine.

The engine is essentially intended to lubricate the moving components inside the engine. The purpose is to ensure smooth running, gliding, and sliding of metal surfaces against each other and to keep friction and heat at a normal level.

The coolant, on the other hand, is designed to keep the car at normal temperature, therefore, preventing overheating.

However, if the fluids mix, the consequences are devastating on the engine. The engine can knock but will start with overheating.

So, make sure you separate the coolant from the engine if you suspect that they’ve mixed. Fix any leaks

3. Can You Drive Subaru EJ25 Car With Spun Rod Bearing?

No. Here’s the thing: a spun bearing usually will clog the flow of oil and oil pressure to the journal and bearing surfaces.

Hence, if you continue to drive your car with the spun rod bearing, it’ll damage the turbo and that will cost you a lot of money.

Additionally, other terrible results will follow, including oil pump failure and melting of the camshaft to the journal.

If you notice that the rod bearing has become spun, the best thing is to have your local mechanic take a look at the engine and resolve the issue as soon as possible.

If you don’t have the money for repair- which is usually high- it is better to park the car in the garage until the problem is fixed.

To fix spun rod bearing in your Subaru EJ25, you should set aside something in the region of $500 to $3000.

Final Thoughts

Subaru EJ25 problems may vary from one another, just as you will find in other car models. Overall,

I will advise users to always opt for OEM parts to solve the above problems I have discussed and shun the use of aftermarket parts. No doubt, the Subaru EJ25 engine is a reliable model on the market.


Written by Kane Dan

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