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Over the years, there have been countless stories about Subaru engines and their reliability. But it’s a myth that Subaru engines will blow up for no reason. In fact, there are reasons behind the glut of engine failures in the Japanese brand’s cars from 1996 to 2005. And between decades of research and aftermarket development, it turns out you can stop blowing up Subaru engines by making just two changes.

Why do Subaru engines blow up?

Derived from a 2.2-liter four-cylinder Boxer engine, the later Subaru 2.5 engine had a penchant for blowing up. Simply put, rather than extending both the stroke and bore of the cylinders, Subaru elected to simply expand the bores. That meant thinner cylinder walls and, therefore, more pronounced cylinder deflection under load.

This, combined with the open-deck engine construction, meant more pronounced movement in the cylinder walls.

As such, the head gaskets are under more stress and experience more friction. In turn, the gaskets wear out quickly, causing coolant leaks. Undetected, these coolant leaks cause engine damage and overheating that can cause the engine to fail spectacularly.

Make your Subaru engine more reliable with a head gasket upgrade

These historic Subaru rally cars have a mix of open and semi-closed deck engines
Subaru Festival | Subaru

Both the original composite head gaskets and revised, graphite-coated gaskets couldn’t handle the additional deflection in the cylinder walls under heavy acceleration. As such, these gaskets would fail at 100,000 miles, if not sooner. When caught early, the head gasket itself could be swapped for a new one.

Unfortunately, if the old gasket is replaced by one of the same type, the failure will happen again. Furthermore, if the mating surfaces are improperly prepared, the subsequent failure will happen even more quickly.

However, aftermarket companies like Fel-pro and Six Star make more durable head gaskets that improve the reliability of the engine as a whole. These components are made from multi-layer steel that is more reliable than the gaskets from Subaru. In addition, proprietary coatings and advanced sealing technology outperform OEM components and make your Subaru 2.5 engine more reliable.

These aftermarket gaskets outperform the standard Subaru kit and prevent the subsequent problems that result from blown head gaskets. However, the gasket alone isn’t enough to ensure the problem doesn’t pop up again.

It’s also critical to ensure that the cylinder head is properly machined to be perfectly flat. Removing all of the old gasket residue and debris is paramount to ensuring that the new gasket seals properly. As such, it’s important to know that the mechanic you’re working with has the skills to do the job the right way.

Coolant conditioner aids in Subaru engine reliability

New Subaru Boxer engine, which is less prone to blow up
Subaru Boxer Engine | Christopher Evans/MediaNews Group/Boston Herald via Getty Images

In any engine, the cooling system also acts as a ground for the battery. That said, cars with early 2.5-liter Subaru engines didn’t have enough physical grounds to balance out the system. That meant more charge going through the cooling system when the battery was low on power.

This started a process called electrolysis, where electricty changes the chemical composition of a substance. In this case, it raised the pH of the coolant, causing corrosion to internal engine parts and gaskets.

However, Subaru offers a coolant conditioner to help offset this problem. This helps reduce the risk of electrolysis to prevent corrosion inside the engine. Furthermore, the brand recommends specific coolant and system maintenance to further reduce the risks.

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