Subaru Catalytic Converter Problems

by Jody L. Campbell

Subaru Motors has employed multiple catalytic converters on its vehicles for many years now. Because the engine compartments are small and since the catalysts need heat to operate effectively, Subaru designed smaller converters and integrated them into the exhaust pipes--rather then employ a single, larger converter as most cars did at one time.

The Structure and Design

Many converters on Subarus begin at a front Y-pipe that bolts to both sides of the engine. In some newer applications, a third or fourth smaller converter is also integrated into the construction of the pipe. It is not uncommon to see yet another converter downstream integrated in the construction of an intermediate pipe. With so many converters, one of them is bound to need replacement at some point.

The walls of the shell on the Subaru converters are designed thin in order to reduce the resistance of exhaust gases. While this benefits the performance of the engine, it compromises the structural durability of the shell. In addition, since the converters are often integrated into the construction of the Y, or intermediate exhaust pipes, the pipe extensions can fail, requiring the replacement of the entire pipe and converter assembly.

Another more slightly annoying feature Subaru owners discover about the exhaust system on their vehicles are heat shield rattles. Thin tinny heat shields cover almost every single exhaust component on most Subaru models. These heat shields are susceptible to exposure and can break loose from connections and create annoying rattles while driving.


Because of the integration of the pipe and converter assemblies, Subaru converters are very expensive. The front Y-pipe assemblies can cost twice as much money to replace as the rear converter assembly. Many owners not savvy enough to do the work, will have to dish out money for labor installation as well.

While there are many quality aftermarket catalytic converter manufacturers these days, you can price the converters and pay less than half what the Subaru dealer will be asking. Finding a local repair station to install it for you will still save you money in the long run.

Although much cheaper, universal converters are not always an option when it comes to a Subaru. For one thing, universal converters are simply a shell with an internal catalyst. They need to be welded into the system are attached by clamps and sleeves. Because of the awkward angles and the small size of the Subaru converters--especially in the front Y-pipe--finding the right size and then welding it into the existing pipe without compromising how it needs to bolt to the engine and the remaining exhaust system is very difficult.

Internal Break Down

Subaru vehicles generally run well, and catalytic converters rarely fail unless something causes the damage. Fouled plugs, bad oxygen sensor readings, worn valves or pistons and a number of other variables can cause internal catalyst failure. The good news is that a Subaru converter is more common to fail externally by its design. The bad news is, if you don't take care of your Subaru and it causes damage to one or more of the converters, you now have a bigger problem. Buying and replacing the converters will be expensive enough. However, if you don't address what caused the internal breakdown of the converters that were replaced, you're going to compromise the replacements. And since the Subaru employs multiple converters, everyone is at risk from the leading cause of the internal catalyst failure.

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