Subaru Head Gasket Issues Explained

It’s not uncommon for certain cars to develop a reputation for a specific issue, but there may not be a more well-known failure point in the car industry than Subaru’s infamous head gasket issues. 

While the brand has largely eliminated this problem on their modern vehicles, there was a period of time when head gaskets in Subarus were seen almost as guaranteed wear-items rather than dependable factory components. 

In this article, we’ll explore why these issues became so prevalent, the models affected, and what you can do to protect your Subaru.

What Are Head Gaskets?

Head gaskets are the seals that sit between the engine block and cylinder head(s). They are responsible for keeping the combustion gasses within the combustion chamber, sealing coolant and oil passages, and stopping coolant and oil from mixing or entering the cylinders. 

When a head gasket blows it fails to form a complete seal, and can allow for coolant and oil to mix, and the combustion chamber to leak internally. A failed head gasket can also lead to lost compression, which will lead to lots of other issues. 

Head gasket failure can cause a whole host of problems for your motor. Your engine may begin to burn off coolant or experience contaminated oil. A blown head gasket can result in severe overheating and potentially critical engine damage. 

Head gasket

Affected Models

Unfortunately, this issue wasn’t isolated to one particular model, or even one motor, in Subaru’s lineup. 

Since the issue was so common and well-documented though, we actually have a pretty robust system for breaking down which engines were affected and why.

We can break down the whole list of models with the problematic gaskets into two main groups.

Group 1

Group 1 includes the models equipped with Subaru’s first-generation 2.5L EJ25D DOHC boxer engine. 

Many claim it was the boxer layout that caused the rapid degradation of gaskets. Boxer-style engines use horizontal pistons rather than vertical, which allows the coolant to pool up against the side of the gasket while the engine is off. This allows for the acidity of the coolant to eat away at the graphite film around the steel gasket and cause failure. 

The blame may also fall more on the gasket itself. Subaru switched from composite gaskets to steel gaskets with the outer graphite film for this engine. While the coolant may eat away at the material, some say the material itself was flawed anyway and bound to flake off over time. 

The preliminary signs of head gasket failure in an EJ25D vehicle include an oily film and possibly a fuel or sulfur smell found in the coolant overflow tank. 

Models affected:

  • 1998 Subaru Forster
  • 1998 Subaru Impreza
  • 1996-1998 Subaru Legacy GT/LSi/Outback

Group 2

Subaru’s EJ boxer lineup continued to be plagued by head gasket issues following the EJ25D. The SOHC EJ251, EJ252, and EJ253 all were noted to have the same failure in the graphite film used in the gasket. However, these motors saw a higher rate of external leaks compared to internal leaks, which meant the issue was not usually as severe as the internal leaks of the EJ25D.

Subaru EJ251 engine bay
Fletcher6, CC BY-SA 3.0, via Wikimedia Commons

Although many of the leaks were external, the issue was more widespread this time around as these motors were fitted to a wider range of models. 

Models affected:

  • 1998-2003 Subaru Impreza
  • 1998-2004 Subaru Forester
  • 1999-2004 Subaru Legacy
  • 2000-2004 Subaru Outback

Other Models & Engines

Beyond the ones listed above, there were some other models and trims equipped with problematic EJ motors, including the second generation 2.2L EJ22 fitted in some late 90s Subarus.

There’s no exact model year we can prove is the one in which they “fixed” the issue. Subaru vehicles continued to be prone to failures for years, even beyond the most affected generations. However, answers range from the 2005 model year and above all the way until 2012, when Subaru redesigned its 2.5L boxer and is believed to have entirely fixed the issue. 

Symptoms of Blown Head Gasket

If your Subaru has blown its head gasket, you may start to experience these issues:

  • Thick white smoke from the exhaust
  • Reduced power
  • “Milky” contaminated oil
  • Overheating
  • Bubbles in coolant reservoir

How to Avoid Head Gasket Failure

If you want to protect your head gasket for as long as possible, there are some steps you can take to prolong its replacement. 

Consistent Oil Changes

Since engines are not able to burn 100% of their fuel, the leftover residue can begin to mix with your oil. Fuel is a solvent, and when mixed with your oil, will eat away at your head gasket. Change it at frequent intervals to slow down the damaging effects.

Keep Your Coolant Fresh

Similar to engine oil, coolant can also become corrosive with time. Keeping your coolant fresh will prevent it from having the chance to degrade your gasket.

Some claim that this era of Subaru vehicles has a problem with electrolysis occurring in the coolant, which causes it to become corrosive. Electrolysis happens when an electrical current runs through the coolant and leads to a chemical reaction in which the acidity increases. 

Subaru Maintenance and Repair in Ann Arbor

Whether your Subaru model is one prone to gasket failure or not, preventative maintenance is crucial for protecting your vehicle and ensuring it’s running at its best. The Subaru experts at Orion Automotive Services in Ann Arbor have the experience and equipment to properly take care of your vehicle! Call or schedule online with us today.

Book with our certified technicians today!


Book with our certified technicians today!