Why Do Subarus Blow Head Gaskets?

Subarus are well-known for their all-wheel-drive systems and ability to navigate tough terrain and snowy highways. However, numerous Subaru models from the 1990s and 2000s have a reputation for blowing head gaskets. Why do Subarus blow head gaskets?

The main cause of this problem was inadequacies in Subaru’s head gasket designs throughout those years. During heating and cooling cycles, the aluminum heads and iron engine blocks expanded and contracted differently. This eventually led the head gaskets to fail prematurely. When the head gaskets started to leak, compression in the cylinders was lost, allowing coolant to enter the engine. If a burst head gasket is not fixed, it can cause damage to other engine components such as the cylinders and the head. While Subaru has improved its designs and manufacturing processes, several of its older models continue to be problematic. 

Why Do Subarus Blow Head Gaskets?

Subarus are recognized for their dependability, although head gasket failures are a prevalent problem with certain versions. Several reasons contribute to this issue:

Boxer Engine Design

Subarus often have boxer engines with horizontally opposed cylinders. This design can cause uneven heating and cooling of the engine, putting additional stress on the head gaskets.

Material Mismatch

Subaru engines frequently have aluminum cylinder heads and cast-iron engine blocks. When these materials are subjected to heat, they expand and contract at varying rates, putting strain on the head gaskets over time.

Cooling System Issues

Inadequate cooling system maintenance, such as low coolant levels, outdated coolant, or a broken thermostat, can result in overheating. Excessive heat can cause the head gaskets to degrade and fail.

High Mileage and Age

As Subarus age and accrue mileage, wear and tear on engine components, especially head gaskets, becomes increasingly noticeable. Over time, the gaskets may develop leaks or disintegrate completely.

Quality Control

While Subaru automobiles are typically well-built, some models may have experienced problems with head gaskets due to manufacturing flaws or anomalies in quality control systems.

Symptoms Of Blown Head Gasket

A blown head gasket can cause a variety of symptoms. Common indicators of a burst head gasket are:


A sudden increase in engine temperature or repeated overheating might be a clear sign of a burst head gasket. The damaged seal causes coolant to leak into the combustion chambers or oil passageways, resulting in ineffective cooling.

White smoke from the exhaust

If you see thick white smoke coming from the exhaust pipe, it could be coolant leaking into the combustion chambers and burning with the fuel. It produces white exhaust emissions.

Milky oil

A burst head gasket can mix coolant with engine oil, causing a milky or foamy look on the dipstick or oil cap. This contamination lowers the oil’s lubricating capabilities and, if not treated promptly, might cause engine damage.

Loss of coolant

A fast reduction in coolant level with no visible leaks or puddles could signal a head gasket leak. This allows coolant to exit into the engine or exhaust system.

Poor engine performance

A burst head gasket may cause misfires, rough idling, or a discernible loss of engine power. It is a result of the weakened seal lowering the efficiency of combustion.

Pressurized cooling system

The cooling system may experience an overabundance of pressure due to a blown head gasket. This can result in radiator or hose ruptures, coolant overflow, or coolant leaks.

External coolant leaks

Puddles or drips beneath the car may indicate an external coolant leak caused by a burst head gasket.

It is possible to stop additional engine damage and expensive repairs by identifying these signs early and taking appropriate action. You can hire the mechanic to check your car if you think there may be a blown head gasket.

How To Fix Blown Head Gasket?

You can follow these methods to fix a blown head gasket:


Confirm that the head gasket has blown by doing a comprehensive inspection and diagnostic testing. Symptoms of a blown head gasket include overheating, coolant leakage, white smoke from the exhaust, and milky oil.

Assess Damage

Determine the severity of the damage caused by the blown head gasket. You should check the cylinder head, engine block, and other components for cracks, warping, and other defects.


To access the head gasket, you must first remove the engine’s concerned components. This necessitates careful dismantling of the engine.


Thoroughly clean the cylinder head and engine block surfaces where the head gasket is installed. Any residue or debris must be removed to guarantee a good seal.


Install a new head gasket, making sure it is the proper type and size for your vehicle’s engine. Replace any broken or worn components, including cylinder head bolts and seals.


If the cylinder head or engine block shows symptoms of warping, they may require resurfacing to provide a level and smooth sealing surface.


Carefully reassemble the engine components in the reverse sequence of disassembly, following the manufacturer’s instructions. This involves reinstalling the cylinder head, timing components, and any other previously removed parts.


Once the reassembly is complete, run a series of tests to check the repair was successful. You must ensure that the head gasket seals properly and there are no leaks.

Fluid Replacement

Replace engine oil and coolant to prevent contamination from coolant or other repair debris.

Final Inspection

After completing the repair, thoroughly inspect the engine for any leaks, unusual noises, or other problems. Road test the car to confirm it functions effectively in a variety of driving circumstances.

Repairing a blown head gasket is a difficult and labor-intensive task that necessitates experience and specific gear. To ensure a reliable repair, proper processes must be followed and high-quality replacement parts used. If you’re not familiar with engine maintenance, you should leave this task to a professional mechanic.

How To Avoid Head Gasket Failure?

Proactive maintenance and routine inspection are necessary to prevent head gasket failure. The following actions can help prevent head gasket failure:

Follow Manufacturer’s Maintenance Schedule

Adhering to the recommended maintenance intervals indicated in your vehicle’s owner’s manual is essential. Regular maintenance improves engine performance and prevents problems that could lead to head gasket failure.

Monitor Coolant Levels And Condition

Check coolant levels on a regular basis, and look for signs of contamination or leakage. Coolant should be replenished as needed with the type prescribed by the manufacturer. Also, make sure the coolant composition is accurate and there are no air bubbles stuck in the system.

Maintain Proper Engine Temperature

Monitoring the engine temperature gauge and resolving any abnormalities as soon as possible will help prevent overheating. Replace worn thermostats, radiator caps, and other cooling system components as suggested. Avoid driving for long periods of time with an overheating engine, as this increases the likelihood of head gasket failure.

Use High-Quality Coolant

Use the manufacturer’s recommended coolant and be sure it’s compatible with your vehicle’s cooling system. Avoid combining various types of coolant. This can cause chemical reactions and potential damage to the head gasket and other engine components.

Address Engine Problems Promptly

Misfires, rough idling, and power loss should all be addressed as soon as they occur in the engine. Ignoring these symptoms can cause further stress on the head gasket and other engine components.

Avoid Aggressive Driving

Driving habits might affect engine stress and temperature. Avoid over revving, high-speed driving, and heavy towing or hauling.  These actions can put undue strain on the engine, increasing the likelihood of head gasket rupture.

Inspect And Maintain The Cooling System

Inspect hoses, belts, and other cooling system components on a regular basis for signs of wear and damage. Replace any worn or broken parts to prevent coolant leaks and maintain optimum cooling system operation.

Following these preventive actions can dramatically minimize the likelihood of head gasket failure and extend the engine life of your car.

What Does Head Gasket Replacement Subaru Cost?

Head gasket replacement cost for a Subaru can range from $1,500-$3,500 depending on the make and model of the vehicle. Labor is the primary expense, as removing the head from the engine block to access the gaskets is a time-consuming multi-hour process. 

Parts including new head gaskets, possible head resurfacing, timing components and cooling system fluids also drive the bill upwards. Shop rates for mechanics specialized in Subaru repairs combined with the complexity of the repair result in a job that is cost-prohibitive for some owners depending on the value of the vehicle. While costly, replacing failed head gaskets is usually necessary to avoid further engine damage and get problem-plagued older Subaru models back on the road smoothly.

Leave a Comment