You may have heard rumors of Subaru head gasket problems. The term “Subaru weak head gasket” often comes up on forums and other sites.
So, what’s the truth about this topic? And what should you do if you have a problem?
Or perhaps you’ve discovered one of the chilling, tell-tale signs that the head gasket has blown.
Whatever your reason for reading this article today, we hope you find something useful here.
To begin with, we will be looking at Subaru engines and general information about head gaskets. After that, we will look at some common Subaru head gasket problems and the solutions.
- Just How Reliable Are Subaru?
- Head Gasket Replacement Cost
- 2019 Subaru Impreza 2.0i SE Lineartronic Review
Subaru. Perhaps the best-known company when we think about road-legal rally cars. The Impreza, in particular, is almost impossible to think about without the mind flashing through images of Colin McRae flying through the air, engine screaming.
The public image of Subaru cars – Imprezas in particular – is, undeniably, sometimes associated with class divides. The wide-bore exhausts and Boxer-4 engines aren’t exactly subtle or discreet. Neighbors might understandably not be huge fans.
This is all true, however, this shouldn’t take away from the genius of Subaru cars.
In particular, we will be considering the Boxer (or “Flat”) engines used in these vehicles.
Nowadays, these engines belong to somewhat of a niche group, although a few cars have had them in the past. This includes the famous Citroen 2CV. It was originally designed by Karl Benz with only two cylinders and was named the Contra Engine.
Click here to check out an article on Sport Subaru that talks about these engines in greater detail.
What Are Some Other Common Subaru Problems?
Before delving into Subaru head gasket problems, we’ll briefly touch on a couple of other issues you might face.
Many of these are centered around certain rubber components of the vehicle.
As we will look at, Subaru head gaskets blowing are far from uncommon.
This is a problem that is certainly not unique to Subarus. All cars will go through this, especially those in areas with low-quality roads and/or hot, dry climates.
Front suspension is almost always under more stress, at all times. This is because the engine is almost always located at the front of the car, especially for cars powered by internal combustion engines. There are, of course, a few exceptions to this.
The front suspension is also constantly under stress. When you approach a bump in the road and put the brakes on, the weight of the car is thrown to the front of the car. This is called “dive”. When you hit the bump, the majority of the weight of the car is there at the front, putting the suspension here under a great amount of force.
When the car goes in for a service, you should make sure that the front suspension is thoroughly checked. This includes the rubber components.
Air Conditioning O-Rings
You’ll know your air conditioning isn’t working if, well, it isn’t working. You’ll notice hot, humid air coming through the vents when your AC is on – clearly, something is wrong.
Sometimes your car will just need a re-gas. Taking the car to a qualified technician should solve your problem here. However, the technician may find a leak. Should this happen, you’ll need to take the car to an automotive air conditioning specialist.
The problem with the AC system could likely be the O-Rings. O-Rings are the rubber seals of the air conditioning system. Over time, these may begin to become brittle and degrade, meaning the system won’t work.
This video describes what O-Rings are and where they go, although we wouldn’t recommend installing them yourself. The refrigerants used in air conditioning systems are toxic and illegal to let out into the atmosphere. The job should be left to a specialist.
To avoid this, try leaving your AC on all the time. Even during winter, but with the temperature on maximum. Sometimes, this might not be practically possible, such as in extreme negative temperatures, but you should do it if possible.
This is because the O-Rings are designed to be constantly lubricated. Turning your air conditioning off for half the year can lead to them becoming brittle. Keeping it on all the time will help them to last longer, as well as being better for your car’s interior.
Again, this is far from a “Subaru-only” problem.
Turbo failure is always going to be quite costly and, as more and more cars come with built-in turbochargers (for environmental reasons, predominantly), this becomes ever-more present in a wider range of cars.
Expect to pay out over $1,000 including labor to get a good-quality new one.
Boxer Engines (Flat Engines)
These engines are either referred to as Boxer engines or flat engines. For this article, we’ll stick with the term Boxer engine.
They are “horizontally opposed” engines. Only two car companies in the world use this type of engine, these being Subaru and Porsche.
Subaru is a unique company, because Boxer engines are used in every single car it makes. Literally. Subaru is the only major car company that rigidly stands by an original concept. This makes it one of the only car companies in the world to rigidly maintain its identity, while also adapting to an ever-changing market. For this reason, we have a lot of admiration for the company.
Boxer engines have cylinders that lie down flat and reciprocate in opposite directions. It is so named because of how similar it looks to a boxer (like Muhammad Ali or Mike Tyson) punching out.
The Boxer engine is unquestionably (in my opinion) the best commercially available engine if you’re looking for performance. In terms of maintenance and upkeep, well, it’s a little bit irritating. But if you are a die-hard Subaru fan, these engines are worth all the niggles and problems.
These increased levels of performance come from the concept of smoothness. In the mechanical world, the smoother something is (the more efficient it is), the better the power output will be.
In other typical internal combustion engine (ICE) setups, such as inline (also known as “straight”), V-engines, or W-engines, the balance needs to be adjusted in one way or another.
You may have been in a situation before where the car begins vibrating excessively. In this situation, opening the hood often reveals a shaking engine block. The cause is usually a misfire, meaning that one cylinder isn’t firing. This makes the forces unbalanced and, as a result, you get all that shaking, vibrating, and noise. This shows the importance of having a correctly balanced engine.
Inline-4 engines, for example, have balanced forces in the horizontal plane, but don’t in the vertical. Inline-3 engines, though, don’t. Like V- and W-engines, they need components called balancing shafts to force the forces (ha) to balance out.
Boxer engines, though, balance perfectly, without the need for extra interference from engineers. From this, you get smooth, unadulterated power.
(They are almost always built with four or six cylinders.)
Advantages of Boxer Engines
There are also other pros. Driving a car with a Boxer engine (almost certainly either a Subaru or a Porsche) yields the following benefits.
- Improved balance (compared to other engine setups), which leads to greater levels of power and, importantly, control.
- The fact that the engine is flat means that the engine’s output can go straight into the transmission. Therefore there are fewer components needed to transfer power, meaning less energy is lost in the process. This is related to the increased levels of fuel economy. It also means that the engine can sit right on the centerline of the car. For most cars with inline engines and mounted across the engine bay, the transmission attaches onto the side. This creates a slight weight imbalance in itself.
- Increased fuel mileage – compared to other American all-wheel drive cars, Subaru vehicles often have a better fuel economy. They’ll also commonly match levels seen in front-wheel-drive cars. In other parts of the world, Boxer engines are often seen as being uneconomical, but this is due to the engine size rather than layout. Why build a performance engine that can’t perform? Compared to inline engines of the same size, Boxer engines are usually more efficient.
- The vehicle’s center of mass is lower, leading to increased handling. It’s basic physics. This is because the Boxer engine is laid out “flat”. Click here to learn more about center of mass from Khan Academy.
- Boxer engines are safer in case of a head-on collision. This comes down to the shape, again. Because of its layout, the engine dips below the passenger cabin, rather than smashing back into it. This means that you, as either a passenger or the driver, are less likely to be seriously injured. Having said that, nobody wants to be in a head-on collision in the first place…
- Fewer vibrations – nobody wants to be driving a car with excessive vibrations. Again, this comes back to the intricate balance of the engine, which means fewer not-nice-sounding noises are coming from under your hood.
Disadvantages of Boxer Engines
There aren’t many, but there are certainly a couple of Subaru Boxer engine disadvantages to mention.
- Maintenance – this is probably the main one. In a normal inline engine and most V- engines, changing your spark plugs or working on your camshafts is relatively simple. They’re just sat there at the top of the engine. But, because the cylinders are horizontal on a Boxer engine, you’ll have to work your way in from the side. Both sides. It’s much more fiddly and you can expect to never complete any engine-based maintenance without cursing the car many times over.
- Two lots of everything – the layout of the engine means that there are two engine blocks and cylinder heads. This is perhaps part of the reason for the Subaru’s reputation of having head gasket problems – there are just more things that might go wrong.
- Despite all the benefits, the Boxer engine has a pretty large footprint. This can make it kind of tricky to work in all the space for things like the steering rack.
What Is A Head Gasket?
A head gasket is a vital part of an internal combustion engine. It is a precisely-engineered piece of metal that functions as a seal between the cylinder head and engine block. Usually, it’s made of steel. Originally, they would have been made of fibrous composite material.
The engine block is the big, main bit of your motor. It is bolted onto the frame with engine mounts and contains the pistons. Because it contains these components, the block is subjected to a lot of friction and stress. It has to be lubricated and cooled with built-in motor oil and coolant channels.
The cylinder head is the bit that’s bolted on top of the engine block. Here, the air/fuel mixture is ignited and the piston is driven down in the cylinder. It also contains the camshafts, valves, and spark plugs. Again, this results in extreme forces and high temperatures.
The head gasket sits between these two components.
Its main function is to keep oil, coolant, and intense forces away from the cylinders as they pass between the head and the block. It also keeps oil and coolant channels sealed and away from each other, so everything works perfectly.
If something goes wrong with the head gasket, this is usually referred to as the head gasket “perforating” or, if it’s completely gone, “blowing”.
Watch this video to see it explained in detail.
Subaru cars have two head gaskets. This is because of Boxer engines and their horizontal layouts, with one cylinder head on each side of the engine bay.
At face value, you can think of this as being twice as many components that might go wrong. That would be true, but there is a little more to consider when talking about Subaru head gasket problems. We will continue that train of thought in the section “Why Does My Subaru Head Gasket Develop Problems?”.
What Does It Mean When A Head Gasket Blows?
A head gasket blowing is the main problem you’ll come across with the component.
When you hear the phrase “blown head gasket”, it really just means that the head gasket has failed. Most commonly, this is caused by cracks that develop in it.
It’s called a “blown” head gasket because cracks or holes in the gasket allow pressure to “blow” past it and out of the combustion chamber.
Although it doesn’t or look like much on the surface, a head gasket blowing is a major problem. Major.
This is because, without this little piece of metal, coolant and oil are free to jump into the cylinders and get burned up in the normal combustion process. And why is this bad? Well, because the engine is totally dependent on those things – the things that are now burning and being sent out the exhaust as gas.
Keep scrolling down to “How Do I Know I Have Subaru Head Gasket Problems?” for a list of symptoms you should watch out for. Catching this problem early on could save you a lot of time, money, and inconvenience.
Is My Subaru Head Gasket Weak?
We will look at this in more detail in a moment.
Subaru cars are, unfortunately, known for head gasket problems. This is particularly true in the following models.
- Impreza (1999-2011).
- Forester (1999-2010).
- Legacy (2000-2009).
- Outback (2000-2011)
- Baja (2003-2005).
It is, of course, not solely limited to these cars though.
In the early years of the above-mentioned ranges, Subaru was using a newly-developed steel shim gasket. This is actually harder than most contemporary gaskets. However, this meant that it didn’t adapt so well to surface imperfections on either the head or the block.
As a result, if any of these areas experienced slightly more pressure than another, it could lead to a leak in the gasket.
This doesn’t, in itself, cause the head gasket to fail. But if the engine gets too hot, then is where you might develop a problem, because the head gasket is already weakened in certain spots.
Why Does My Head Gasket Develop Problems?
On the average car (as opposed to, specifically, a Subaru), the head gasket usually blows due to either:
- excessively high temperatures
- excessive wear, or
- faulty original components.
These are written in approximate order of likelihood.
Excessively High Temperatures
This is the most common cause of head gasket failure.
It arises when the engine overheats to beyond the temperature range it was built to withstand. This could happen because of a variety of things.
- Low oil levels.
- Low coolant levels.
- The fuel mixture is too rich.
- Sensor faults or failures.
When the engine block and cylinder head overheat, they can get so hot that the metal they’re made of warps. As the metal warps, it breaks the head gasket as it sits between them.
If this is the cause of your head gasket failure, you need to get the block and head machined down so they’re perfectly level again. Not doing this, and simply taking the engine apart and replacing the head gasket before rebuilding it, means the head gasket will just fail again.
Make sure you find the original cause of the engine overheating, as listed above. Once you find this problem, you can stop it from happening again.
This may be the root cause of your Subaru head gasket problem.
This is a classic example of the need to catch things early when working on cars. The longer you leave the problem, the more knock-on effects it will have.
Remember, an engine is always vibrating. There are strong forces constantly at play.
As the head gasket sits between the block and the head, they are both vibrating. Over time, this can degrade the metal and slowly break it down. Eventually, it’s almost inevitable for the head gasket to blow, if the car has done enough miles.
If excessive wear is the cause of your blown head gasket may have its benefits. If this is why the head gasket has blown, you may not need to get the block or head machined down or fix any other problems.
The head gasket still needs to be replaced though, of course.
Subaru – Faulty Original Components
Faulty original components are the most notorious reason for Subaru head gaskets failing. We will use Subaru as an example to explain this cause.
From 1997 to 1999, Subaru began to use a self-developed head gasket in some models. It was a multi-layer steel shim covered with a graphite layer and wasn’t as effective as many others out there.
There were many benefits to this new steel shim head gasket. It was harder than the aluminum which formed the head and the block and comparatively stronger. Because of this, they don’t compress over time, meaning that they never have to be re-tensioned.
However, steel shim head gaskets are particularly susceptible to surface imperfections. This is a side effect of having an extremely hard gasket. Any slight surface imperfection in the block or head can lead to a disproportionate amount of pressure in that area of the gasket.
Should a situation occur when the engine is running too hot, this can make a leak more likely to develop.
Subaru – Boxer Engine Layout
When we look at inline or V-engines, the fluids drain to below the head gasket level when the engine is switched off. However, in Boxer engines, the fluids rest against the head gasket. If they are corrosive enough, this can eat away at the metal over time.
How Do I Know I Have Subaru Head Gasket Problems?
Head gasket problems usually lead to coolant and/or oil leaking into the combustion chamber. Once this happens, it gets burnt and sent out through the exhaust pipe. You will notice white (coolant) or blue (oil) smoke coming out of the tailpipe. This is a telltale sign of head gasket failure (although it could also represent several other problems).
Don’t get confused with water vapor that may appear to be white smoke on a cold morning.
You will also probably notice the following symptoms.
- Quick oil consumption.
- Quick coolant consumption.
- Regular overheating of the engine.
You might also notice…
- Oil in the coolant.
- A sulfur-like smell coming from the coolant.
- Milky white colors in the motor oil.
Once you notice these, it’s time to get it fixed.
How Do I Fix My Subaru Head Gasket Problem?
Sorry to be the bearer of bad news, but this is usually best left to the professionals. It’s an expensive job – for a Subaru head gasket change, it’ll probably cost well over $1,000. However, getting it done professionally means the cause of the problem can be properly addressed.
A few advanced tools are needed for this job, including an engine heist, a precise level, a precise torque wrench, and very good automotive skills.
If all you did was replace the head gasket, the problem may occur again. The root cause of the head gasket failure needs to be discovered and fixed if you’re to be free of the issue in the future.
We strongly recommend facing the cost on this occasion.
However, if you’re confident with what you’re doing, here is a video showing you how to do it. To give you an idea of the scale of this job, this long video is Part 1 of 5.
Here is a link to Part 2, if you would like to watch the whole series.
What Can I Do To Prevent Subaru Head Gasket Problems?
Essentially, this breaks down to needing to stop your engine from overheating.
You can do this by:
- Regularly changing the engine oil.
- Regularly changing the coolant.
- Checking the oil and coolant levels often.
- Use OEM parts, oils, and coolant.
Should I Get A Subaru?
If that’s where you’re heart is at, yes. Subaru is a brand that has rigidly stuck to part of its identity while maintaining a competitive market share. Although head gasket problems are associated with older models, that shouldn’t put you off.
Newer models are far less infamous when it comes to head gasket problems, so you should take some reassurance from that. Don’t forget to research the CVT problems also.
Owning a Subaru, especially a sportier model, can be expensive – no doubt. But if you’re a fan nevertheless, you could consider swallowing the cost and just enjoying these brilliant pieces of engineering.
These tools have been tried and tested by our team, they are ideal for fixing your car at home.