Why Subaru Engines FAIL

In this video we tear down a Subaru Boxer 2.0L turbocharged engine to see what's inside and how it works! We also examine some of the common failure points on these engines and what to look out for if you are looking for a vehicle with a boxer engine.

The Subaru engine in this video was from an early 2000's Impreza WRX with an EJ20 engine. A boxer 4 cylinder engine has pairs of pistons that are horizontally opposed, lending for good engine balance and a low center of gravity. The disadvantages are that the lubrication system takes a longer time to drain back to the sump, making it challenging to maintain proper oil pressure especially if the oil is run low, in addition to maintenance challenges when working on the engine head, such as valve covers, spark plugs, valve adjustments or head gasket replacement.

Common failure points on these engines include connecting rod bearing failure (due to running too low on oil), oil and coolant mixing together (creating a lack of lubrication) due to head gasket failure, weak head bolts or under torque, oil consumption and ring land failure.

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[silvertbird]

I’ve learned so much from these videos, and I am in no way a mechanic. The toothbrush as a pointer is hilarious, but the delivery is extremely professional; no hemming or hawing, just a flow of expert information. Very impressive.

[kiefershanks]

So, bad maintenance is pretty much the #1 cause of failure. Lack of an oil change/running the oil level down, oil starts failing due to excess heat/contamination which clogs the pick-up tube which causes the engine lubrication system to fail which overheats the heads which causes a headgasket to fail which causes the oil to fail even more which helps the make the piston rings fail even more until you have complete engine failure. So... just check the oil and change at reasonable intervals? Gotcha.

[ammadahmed]

100% do a video on this turbocharger and how it works, I think it would help a lot of people better understand a few things, such as wastegate, wastegate actuator, hot/cold side of the turbo, and it would actually be an interesting watch ngl

[alouisschafer]

Meticulous oil changes, high quality oil and keeping the level up will help them last longer.
And DONT tune them just leave them alone unless you are ready for a full build.

[GDisco]

The early 2.5 engine had the composite head gasket that was known to fail over time. When they were replaced with MLS head gaskets the problem went away. They also had the small 48 mm main bearing. Now, the 2.2L engines were almost indestructible.

[MrKnoxguy]

I really enjoy your tear down videos. You keep up a good pace and you know what you’re doing.

[aussietaipan]

The Subaru DOHC turbo engines in the EJ serious have always used the MLS head gaskets. They do not fail unless the coolant has the incorrect mix of water to anti freeze and the alloy corrodes. The main reasons for coolant to oil mix are turbo seal failures and oil filter cooler failures. Good video of the turbo boxer tear down.

[MrSupernova]

Great engine walkthrough as always! Thanks!

[iangillett]

Great informative video.
I ran from new a 2005 2.0L WRX with a Prodrive performance pack. I ran it for 8 years and 80k miles, with no issues. The key for me was good maintenance, best oil, 97/99 gas (UK octane)

[dorianleclair]

They are good engines if taken care of.
The problem is people constantly launching and redlining the engine like they are in world rally cross.

[hukmai]

+1 for turbocharger video
Bonus for subaru CVT teardown and explanation

[Enigmaafk]

The professor on engines . Always something to learn on this channel.

[lewisg]

Here are some of the problems we encountered with our two Subarus: flimsy heat shields that self destruct; exhaust manifolds that pass directly over the CV boots that cooks the rubber necessitating replacement of the entire CV joint; under engineered front disks that warp (replacement with after market disks solved problem); four speed transmissions that downshifted constantly to be replaced by CVT that has its own problems; inherent engineering deficiencies in the engine that commonly results in head gasket and cylinder over-heating problems not found in other four-bangers. The failure of window design (perhaps improved now) made wind noise irritating and the air venting that introduced very warm air into the cabin (necessitating use of AC even with cool outside temps) was just another problem.

[gabrielksh]

that seems like an EJ without a proper maintenance for a long period of time. not the actual subaru engine fail. dont mislead the public with such kind of headline. However u have the best explanation about EJ engine.

[Dansk]

The best breakdown I've seen of a boxer. Learned quite a bit. Keep it up. You'll hit 500k soon!

[officaldjflo]

Mostly cylinder number 4 because of the lack of cooling . The headgaskets ports are smaller than the ones one block. The biggest re among is because the exhaust ports on 2 and 4 are not symmetrical. They bend left and right efore exiting into the exhaust. Which then heat soaks the block. Also cylinder number 4 is the guinea pig for the rest of engine because of the knock sensor is located by 4. Hope this helps.

[lorrinbarth]

This surprises me. The 2L WRX engine of this era with the metal head gasket wasn't known for head gasket failure. NA engines with the composite head gasket always blew. Still, you could expect to get maybe a 100K miles or more before failure. As of a couple of years ago Subaru was still selling this garbage head gasket as a repair part. BTW, this is an interference engine. Extreme care is required when swapping timing belts.

[lihisluikku]

Why subaru WRX engines fail:
1. No maintenance. Like checking oil level even once a week, and changing oil regularly goes a loooong way.
2. Excessive mods. Subies are easy to mod, but the stock engine isn't built to handle more boost than it has stock.
3. It goes fast, so owners redline the car and drop the clutch to launch really fast. I know a guy who does this at practically every green light with his WRX.

And often at least two of those three are combined. Sometimes even all three. The car is tortured, often boosted over what the engine and transmission can take, and regular maintenance is a distant dream.

[jetsetjoey]

Boxer engines have inherent flaws, too; they are notorious for oil leaks, head gasket failures & oblong cylinder wear- due to the forces of gravity acting on the pistons...

[JohnSmith-yveq]

The coolant supply to the body of the turbocharger is there to cool the centre bearing of the
So the turbo, when the engine is switched off after a long hard run, and there is no oil
the coolant will take away the heat and stop the oil in the turbo bearings from turning into carbon...
This became the solution to stop idling down (turbo timer anyone?) ...after people who didn't know any better had cooked the centre bearing with coked up (carbonised) oil....