Subaru Head Gasket Problems (Which Years to Avoid)

Some Subarus have a reputation for eating head gaskets at a very low mileage. Where did this reputation come from?

Though there was never an official Subaru head gasket recall, the problem is pervasive enough where it can be expected that certain original head gaskets will fail between 100,000 and 150,000 miles (160-241k kilometers).

This may sound like a long time, but considering most Subaru owners like to keep their vehicles on the road upwards of 250,000 miles, it’s a pretty big deal. On top of that, the repair is pretty expensive.

Years and Models Affected

Subaru head gasket problem

The main problem years are 1996 through 2004. The most common engine to have head gasket failures is the naturally aspirated (non turbo) Subaru 2.5 L four cylinder engine, commonly known as the EJ25 motor.

The single overhead camshaft (SOHC) variant experiences failures much more frequently than the dual overhead camshaft design (DOHC). The SOHC motors can be identified by their single circular indent on each side of the engine. However, DOHC engines produced between 1996 and 1999 have also been known to leak.

The naturally aspirated EJ25 engine was used across Subaru’s lineup and can be found in the non-turbo Baja, Forester, Impreza, Legacy, and Outback.

Head gasket failures are less common on the Subaru 3.0 and 3.6 L H6 models like the Tribeca. They are also rare on the turbo models such as the turbo Baja, Impreza WRX, and Impreza WRX STI.

Symptoms of a Subaru Head Gasket Leak

head gasket leak
The black carbon deposit on the bottom of cylinder #4 (right) is a textbook symptom of a head gasket leak.

Many symptoms of a head gasket leak on a Subaru are very similar to head gasket leaks on other vehicles.

1) Oil Leak

oil leak

A blown head gasket can manifest in several ways. On first generation Outbacks and second generation Legacy models, the gaskets tend to leak externally. You may notice oil leaks between the head and the block of the engine.

2) Heater Blows Cold

heater blows cold air

Many Subaru cooling systems route their heater core in such a way that the heater will blow cold air when you have air in the heater core.

Assuming the cooling system was bled correctly, air in the heater core is almost always caused by a head gasket leak. This issue is common on second generation Outbacks, as those leaks tend to be internal.

3) Overheating

engine overheating symptoms

One of the telltale symptoms of a head gasket leak is an overheating engine. If your engine starts to overheat, pull over to let it cool down for a bit before you continue driving.

An overheated engine could cause more engine damage and a more expensive repair bill.

4) White Exhaust Smoke

white smoke from exhaust

If you notice a thick cloud of white smoke out of the exhaust that persists after initial startup, you probably have a head gasket leak. However, just because you don’t notice excessive white smoke doesn’t mean you’re leak free.

5) Foamy Oil Cap

foam on oil cap

Does the underside of your oil cap look like black coffee or a Starbucks Frappuccino? If it’s the latter, that’s a warning sign that coolant has leaked into the oil system.

Coolant and oil don’t like to mix and often produce a milky foam when they come in contact.

6) Bubbles in Overflow Reservoir

coolant overflow tank

There should be no air in the cooling system. An overflow reservoir that bubbles while the engine is running is a sure sign that something isn’t right.

While you’re in there, check to make sure the radiator cap is good, as a bad cap could behave similarly.

7) Hydrocarbons in Radiator

bad radiator cap symptoms

Hydrocarbons are produced when gases ignite in the combustion chamber. If you discover these in the radiator, it could mean your head gasket is leaking combustion gases into the cooling system.

You may notice a burnt oil or fuel smell coming from the radiator or coolant overflow reservoir. If you notice this unusual smell, it may be a good idea to have the cooling system tested as soon as you can.

Head Gasket FAQ

What is a Head Gasket?

MLS head gasket

A head gasket provides the sealing surface between the cylinder head and the block. This skinny part has a very difficult job. It needs to keep coolant in the water jackets, oil in the oil passages, and combustion gasses out of the cooling system. It must do this job at a wide variety of temperatures, from cold start to normal operating temperature.

Some head gaskets are a composite made out of other materials such as paper or graphite. Most modern head gaskets are made out of multi-layer steel (MLS).

What Causes a Head Gasket Leak?

head gasket leak
Notice how the blue gasket material is eaten away on cylinder #4 (top right). This allows combustion gases to enter the cooling system.

There is a lot of speculation on the exact cause of Subaru’s widespread head gasket leaks.

Some suggested causes have been low quality head gasket material, poor engine maintenance, bad head gasket design, bad water jacket design, detonation, improper head torque procedures, and electrolysis of the coolant due to poor grounding.

The true cause is likely some combination of these reasons.

How Can I Test My Head Gaskets?

low compression causes

There are several ways you can test the integrity of your cooling system and combustion chamber.

A leak down test is a sure fire way to know if you have a head gasket leak. This test will tell you if any combustion gases are able to escape into the cooling system, or elsewhere in the vehicle while the combustion chamber is supposed to be sealed.

If you see bubbles coming from the radiator filler neck or overflow reservoir while performing a leak down test, you have a head gasket leak.

A radiator pressure test ensures you have no leaks in the cooling system. This test attaches to the radiator filler neck and pumps the amount of pressure your system is designed to hold. If the system won’t hold pressure, you have a leak somewhere.

Radiator hydrocarbon test kits will tell you if hydrocarbon deposits have made their way into the cooling system. Be aware that this test could give you a false positive if the head gasket has ever leaked in the past, even if it has been repaired. You may also get a false positive if you’ve used a petroleum based additive in the radiator.

Do Subarus Still Have Head Gasket Issues?

Over the years the EJ25 engine’s design was revised and gradually phased out. So what year did Subaru fix this problem?

While there is no definitive “safe” year, head gasket leaks tend to be much less common on newer models. If your Subaru is a 2012 or newer, odds are really good that you won’t have any issues.

Can You Drive With a Blown Head Gasket?

head gasket leak
This Subaru drove over 100 miles with a leaky head gasket. The leak wasn’t too bad, so damage is minimal.

Driving with a blown head gasket is not advisable. The longer the issue persists, the worse it gets. Driving with leaky head gaskets will ultimately cause more engine damage and a higher repair bill in the long run.

In an emergency, leaky head gaskets will probably not prevent you from driving the vehicle, especially if the leak is minor. Watch your coolant temperature gauge closely, as you will likely overheat the engine if you drive for an extended period of time.

Overheating an engine could warp the heads, rendering them unsalvageable. If the heads cannot be resurfaced, replacement heads will not be cheap.

How Much Does a Head Gasket Replacement Cost?

While replacement head gaskets are pretty cheap (around $100), the cost of labor is not. Repair estimates commonly exceed $1,500, depending on the extent of the damage and what other maintenance is performed while the mechanic is in there.

Hold Up… Why Is This So Expensive?

Subaru head bolts

Since boxer engines are so wide, many mechanics remove the engine entirely to perform this repair. Removing the engine makes it much easier to extract the head bolts in particular, which are very long and won’t clear the body with the engine sitting normally inside the engine bay.

Subaru short block

To reach the head gaskets, a mechanic has to tear the engine down to the short block. Both gaskets are typically replaced at the same time. When one head gasket leaks, the other is usually not far behind.

If your car is in the shop for a head gasket repair, consider having them change the timing belt, water pump, idler pulleys, cam seals, both main seals, and the front transmission seal if you’re not sure when they were last replaced. 

You’re probably not keen on adding cost to an already expensive repair bill, but these parts are relatively cheap and hard to access normally. There’s no better time to replace them, and you may end up saving money in the long run with this strategy.

Can I Do This Job Myself?

Whether or not you can do this job yourself depends on a number of factors. You will need to be honest with yourself about your own mechanical abilities, then weigh the pros and cons before diving in.

Estimated Downtime

machined cylinder head
To ensure the new head gaskets last a long time, the head needs to be perfectly flat and smooth.

If this is your daily driver and you don’t have a backup vehicle, you probably won’t want to do this job yourself.

A head gasket replacement is very involved. It is not for the faint-hearted, and not something you can tackle over a weekend.

To do the job right, you will need to send the heads off to a machine shop to be resurfaced. The lead time for this step alone could be several days, possibly more if the shop is busy. Consider budgeting extra time and money for a valve job if the valves have seen better days.

Required Tools

You will need some specialty tools you may not have, such as a torque angle gauge and an engine crane (also known as a cherry picker). An impact wrench will make certain tasks much easier, such as removing the crank pulley bolt.

A quality torque wrench is a must. You will also need a socket set, plus several extensions and universal joint sockets to reach the bell housing fasteners. Don’t forget the factory service manual.

Follow the factory service manual very closely. The head tightening sequence is quite unusual and the torque specs are not the same across all models.

You should be able to purchase all of the necessary tools for less than the cost of taking the vehicle to a shop, if you know what you’re doing. As a bonus, it gives you a great excuse to convince your significant other that it’s time to fill your garage with some sweet new tools.

Other Considerations

Subaru timing belt

Most Subaru engines are interference engines, which means the pistons are able to contact the valves if the engine is not timed correctly. This would cause enough damage to warrant a full engine replacement in the worst case scenario. If you’ve never replaced a timing belt or this risk makes you uncomfortable, it’s best to leave this job to a professional.

If you’re interested in leveling up your home mechanic skills, picking up a cheap Subaru with a known head gasket leak could give you an excellent learning experience. Before purchasing, make sure you have the patience, funds for tools, and a clean, dry space to work. It’s wise to grab a safety conscious buddy to help you out if you’re new to this type of thing.

Remember, few mechanics will be happy if your car shows up on a flatbed with a bunch of parts strewn about the interior because you got yourself in over your head. Do lots of research, and make sure you can really commit to this job before you dive in on your own.

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