7 Serious Subaru EZ30 H6 Engine Problems (Mk. 1 H6 Engine)

I’m going to be honest, I never owned a Subaru with the EZ30 H6 engine, but I’ve had the privilege to drive one occasionally and let me tell you, this engine is special. The sound, the power, the feeling, everything is there. But is it reliable? That’s what we’re here for today!

Doing good and proper research is key if you don’t want to end up in a money pit full of problems. And when it comes to cars, the chances for this scenario are really high. Some cars have a lot of issues, especially Subarus. So, knowing which car is good and which is bad is a real mastery. But you shouldn’t worry because this is why we are here to help you out.

First, we are going to cover the specs of the EZ30 engine, then, we are going to learn more about the Subaru EZ30 engine problems and learn what troubles this engine. Lastly, we will learn more about the applications of this engine. So, let’s get started!

Basic Subaru EZ30 Engine Specs

The Subaru EZ30 engine is a boxer engine that was introduced by Subaru in 2001. This engine was designed to serve the purpose in Subaru’s larger models like the Outback and Legacy.

What is worth noting about this engine is that there are two variations. MK I and MK II. The first engine was the original EZ30 flat-6.

This was a naturally aspirated engine that was heavily inspired by other Subaru engines from the EJ series but the EZ30 featured a smaller bore pitch. So, even though this is a flat-6, the dimensions between the EJ and the EZ are pretty much similar.

The MK II engine followed in 2004. This engine featured a lot of upgrades compared to the original engine. The core was the same but the new version added an active valve lift system to the intake camshaft.

This system is very similar to Porsche’s VarioCam system. The improvement resulted in increased power, as well as better fuel economy.

The cylinder heads for the MK II were also redesigned and included three exhaust ports for each head, instead of the single port on the original engine.

The block was also produced with a new casting process and also used hollow camshafts. These improvements reduced weight by 19.6 lbs.

Nevertheless, here are the full specs of this engine.

  • Configuration: flat-6
  • Displacement: 3.0L
  • Bore: 89.5 mm
  • Stroke: 80 mm
  • Block & Head Material: Aluminum
  • Head Design: DOHC, 4 valves per cylinder
  • Aspiration: Naturally Aspirated
  • Compression Ratio: 10.7
  • Horsepower: 220 hp
  • Torque: 219 lb-ft (297 N-m)

Common Subaru EZ30 Engine Problems

Common problems with the Subaru EZ30 H6 engine:

  • Oil Leaks
  • Prone To Overheat
  • Timing Chain Tensioner Failure
  • High Fuel Consumption
  • Idler Pulley Failure
  • AC Compressor Failure
  • Expensive Maintenance

We listed the most common Subaru EZ30 engine problems, now let’s move on and further elaborate on these issues in detail.

We feel obliged to share the information with you on when and how these problems happen, how serious they are and what are the methods to fix them. So, let’s get started with the problems.

1. Oil Leaks

Oil leaks are one of the most common problems with the EZ30 engine. So, what are oil leaks, and why do they happen?

Well, oil leaks are signs that your engine is losing oil. These oil leaks can come from various places on the engine but in the EZ30 engine, the most common place to develop leaks is the timing cover.

This is an aluminum cover that keeps the timing mechanism protected and safe from the elements. And also makes sure that the timing mechanism is lubricated and no oil escapes.

What is unfortunate, is that the timing cover gasket can often fail and cause oil leaks. Especially at the bottom of the engine.

And the only way to solve this problem is to replace the timing cover gasket. This can be a somewhat expensive process because there is a lot of work in this job.

It could easily cost you $500 or more in labor. This is why we recommend that you beware of these oil leaks since they are expensive to fix.

Now let’s move on to the next Subaru EZ30 engine problems.

2. Prone To Overheat

This engine, just like every other Subaru engine, is very prone to overheat. And when the engine overheats, it means that there will be major spending to get it back to proper working order.

This is the case because when the engine overheats, it will blow a head gasket and this will then require resurfacing the cylinder head.

Not to mention that there are not many of these engines around and finding a head in good condition might also be a challenge if the cylinder head is too far gone. And all this is because of the poor cooling system. 

Also, people install turbochargers on these engines and they don’t upgrade the cooling system. Running a lot of boost with the stock cooling is out of the question.

This is why we recommend upgrading the cooling system with a better-flowing radiator if you want your engine not to overheat.

3. Timing Chain Tensioner Failure

Another famous problem with this engine is the timing chain tensioner failure. So, what is the tensioner and what does it do?

The timing chain tensioner has a simple purpose and that is to keep tension on the timing chain. Without this tensioner, the chain would get loose and wobbly.

This will cause slack and this situation will result in loss of tension and rattling noise. This rattling noise will be present at idle and will disappear as you drive.

But it should not be ignored. Since if you ignore this rattle, the chain could jump and the engine can lose timing.

This will result in engine damage. The cylinder head will have to be refurbished since the valves will get bent.

That’s why we recommend that you don’t ignore this situation because it can total out your engine in the process.

Now let’s move on to the next Subaru EZ30 engine problems.

4. High Fuel Consumption

High fuel consumption when it comes to EZ engines is very common. Although technically 6 cylinders, these engines are not that efficient.

Both the EZ30 and EZ36 tend to consume much more fuel compared to the competitor V6 engines. So, you should keep this in mind before getting one of these engines since their efficiency is not one of the best.

5. Idler Pulley Failure

The EZ30 engine also has problems with the idler pulley for the drive belt. This pulley tends to fail on these engines.

So, what is an idler pulley? Well, the idler pulley as its name implies is like a ring bearing that rotates around a shaft. These idler bearings serve the purpose of belt routing in the engine.

The bearings inside start to fail, and the belt will wobble and create strange noises. Luckily, replacing these components is not that expensive and can be done rather quickly.

6. AC Compressor Failure

Another common failure point on these EZ30, as well as the EZ36 engine, is the AC compressor failure.

The AC compressors are not very reliable on these two engines and they tend to fail more often compared to other Subaru vehicles.

And the AC compressor is not something that is cheap to replace. These units are expensive even on the used market.

So, if you intend to purchase one of these engines, make sure that the AC compressor is working on the car. This way, you will avoid paying thousands of dollars to get the AC back in working condition.

Now let’s move on to the next Subaru EZ30 engine problems.

7. Expensive Maintenance

And the last thing to add is not a issue but a good talking point. And this is because the maintenance on the EZ engine is much higher compared to other Subaru engines.

This is the case because these engines are higher-end boxers. They are not your typical EJ engine that can be found and serviced rather cheaply. Also, they are quite rare to find compared to other Subaru engines.

And also parts are far more expensive compared to the EJ engines that are used in other Subaru models.

Which Models Include The Subaru EZ30 Engine?

Now let’s see which models have the EZ30 engine:

  • 2000 – 2004 Subaru Legacy
  • 2000 – 2004 Subaru Outback
  • 2006 – 2007 Subaru Tribeca


What Are The Common Subaru EX30 Engine Problems?

This engine does not have serious issues. But it has a few problems that can be expensive to fix. These include oil leaks from the timing cover, timing chain tensioner failure, overheating, idler pulley failure, and AC compressor failure. Overall, nothing too serious can destroy the engine except maybe for the timing chain tensioner that has to be replaced when the chain starts to rattle.

Is The Subaru EZ30 Engine Reliable?

This is a very reliable engine. Probably one of the more reliable engines that they introduced in recent times, although this is a more than 20-year-old design as we speak. If you can find one in good condition with low mileage, you can go for it.

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