Why Do Subarus Blow Head Gaskets? Let’s Find Out

Why Do Subarus Blow Head Gaskets – In the earlier years, Subaru engines utilized composite-style head gaskets, which had their limitations due to the compressible fiber material and metal rings. These gaskets required occasional re-tensioning, and any breach in the metal ring could result in a catastrophic failure commonly known as a “blown head gasket.”

Subaru vehicles have garnered a loyal following for their reliability and performance, but there’s a persistent concern that has haunted many owners: the dreaded Subaru head gasket issue.

why do subarus blow head gaskets

By the early 2000s, Subaru had phased in these improved gaskets across their lineup, significantly reducing the incidence of head gasket failures stemming from gasket design weaknesses.

Understanding why Subaru head gaskets fail and the subsequent repercussions are crucial for any Subaru owner or enthusiast.

Why Do Subaru Head Gaskets Fail?

In the past, Subaru engines employed composite-style head gaskets made of compressible fiber with metal rings around critical areas to contain the extreme pressures of combustion. These composite gaskets had their limitations, requiring occasional re-tensioning due to material compression over time.

Any breach in the metal ring could lead to a catastrophic failure, resulting in what’s commonly referred to as a “blown head gasket.”

However, advancements in gasket technology led to the introduction of metal shim-style gaskets, mostly made of thin stainless steel shims or layered steel shims riveted together.

Subaru phased in this more robust gasket style in the mid-’90s, virtually eliminating the issues associated with the older composite gaskets.

Despite the technological advancements, Subaru head gasket issues persisted. The design flaws inherent in horizontally opposed “boxer” engines and open-deck configurations played a significant role.

These engines are more prone to flexing and uneven coolant circulation, leading to increased stress on the head gasket and potential leaks.

Understanding the Subaru Head Gasket Problem

Subaru’s head gasket issues escalated when they introduced composite gaskets in certain models from 1997 to 1999.

These gaskets, made of a multi-layer steel shim coated with a graphite layer, were prone to allowing coolant leaks into the exhaust pressure and combustion chamber.

Though Subaru did not issue a formal recall, they modified cylinder heads and camshaft configurations to mitigate the issue. However, external head gasket leaks persisted.

Symptoms of Subaru Head Gasket Problems

Identifying a failing head gasket in a Subaru is crucial. Symptoms vary but can include:

why do subarus blow head gaskets

  1. Oil trickles between the head and block surfaces, potentially leading to coolant leakage.
  2. A noticeable smell of sulfur or fuel from the coolant reservoir, accompanied by higher coolant temperature readings.
  3. Recurrent engine overheating during extended drives.
  4. White smoke is emitted from the exhaust due to coolant leaking into the cylinders.
  5. Oil or coolant leaks outside of the engine, impacting overall performance and power.

Prevention and Solutions

Regular maintenance plays a pivotal role in preventing Subaru head gasket issues.

Changing engine oil and coolant at recommended intervals helps remove contaminants and prevents overheating, a common cause of head gasket failure.

Moreover, understanding the most common causes of head gasket failures, such as engine overheating, allows owners to take preventive measures. Engine overheating can lead to the expansion or erosion of the head gasket’s components, ultimately causing failure.

Common Mileage and Affected Subaru Models

On average, Subaru head gaskets tend to last around 100,000 miles, but this can vary depending on the year and model. Notably, the naturally aspirated (non-turbo) Subaru 2.5 L four-cylinder engine, known as the EJ25 motor, faced prevalent head gasket failures between 1996 and 2004.

How do you prevent a Subaru head gasket from failing?

Preventing Subaru head gasket failure involves regular maintenance practices. Changing the engine oil regularly is crucial to eliminate unburnt fuel that can infiltrate the engine oil, potentially weakening seals and gaskets.

Fuel acts as a solvent that can compromise these components. Additionally, routine changes of the Subaru’s coolant play a vital role in maintaining the health of the head gasket.

What is the most common cause of a blown head gasket?

Engine overheating stands as the primary cause behind head gasket failures. When an engine overheats, the surrounding materials, including the head gasket, expand beyond their intended capacity.

This excessive expansion can lead to the head gasket’s armor getting crushed or eroded over time, resulting in failure and subsequent leakage.

At what mileage do Subaru head gaskets fail?

Typically, Subaru head gaskets are expected to last around 100,000 miles. However, this mileage can vary based on the specific year and model of your Subaru.

Signs indicating potential head gasket failure include rough engine performance or the engine oil acquiring a milky coloration, which may necessitate head gasket replacement.

Which Subarus have bad head gaskets?

The problematic years for Subaru head gaskets are commonly cited as falling between 1996 and 2004. Among the engines prone to head gasket failures is the naturally aspirated (non-turbo) Subaru 2.5 L four-cylinder engine, known as the EJ25 motor.

This engine variant is notably associated with head gasket issues prevalent during those years.


Subaru’s journey through gasket technology transitions, addressing inherent design flaws, and responding to head gasket issues underscores the complexities faced by the brand.

Awareness and preventive care continue to be key for Subaru owners in maintaining their vehicles and avoiding potential head gasket-related complications.

Subaru’s head gasket issues have been a concern for many owners, stemming from historical design flaws and material limitations. Recognizing the symptoms, understanding preventive measures, and staying vigilant through regular maintenance are key to mitigating the risks associated with these issues.

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