Which Subaru Models Have Engines That Are Prone to Blowing Up?
Whether you’re a regular at Cars and Coffee or you’ve got a friend with a Subaru Outback, you’ve probably heard that Subaru engines blow up…a lot. While we’ve covered some of the reasons why Subaru engines blow up so much, it’s also good to know which Subaru models have the worst engines.
A complete list of the most unreliable Subaru models
Generally speaking, modern Subaru cars are pretty reliable. It isn’t until tuners push the turbocharged cars too far or owners ignore maintenance intervals that the newest cars have problems. But if you’re shopping in the used market, these are the least-reliable Subaru cars you’ll find:
- 1996 – 1998 Subaru Legacy 2.5GT
- 1996 – 2004 Subaru Legacy LSi
- 1996 – 2004 Subaru Legacy Outback
- 1998 – 2004 Subaru Forester
- 1998 – 2003 Subaru Impreza 2.5 RS
- 1998 Subaru Impreza 22B STi
- 1999 – 2004 Subaru Impreza
- 2000 – 2004 Subaru Outback
- 2003 – 2005 Subaru Baja
There are several of Subaru’s most popular models on this list, but unfortunately, these cars were also some of the most problematic.
How the Subaru 2.5 engine design evolved to stop blowing up
Notably, after 2005 the turbocharged versions of the Subaru EJ25 have far fewer instances of failure than the cars that came before. The reasoning is fairly simple, and it has everything to do with how the cylinders are constructed.
The least-reliable Subaru engines feature an “open deck” design. The deck, in this case, is the surface at the top of the cylinder head, where the head gasket meets the engine. Open, closed, and semi-closed monikers explain the gap between the cylinder wall and the engine block.
Open Deck blocks are by far the weakest. In this configuration, there is no support between the cylinder walls and the block, so they can’t handle high internal engine pressures. These forces cause the cylinder walls to flex, which wears away at the head gasket above. Over time, it creates a gap where coolant and oil can mix, ruining the engine. In extreme cases, such as high turbo applications, this lack of support can even lead to complete cylinder failure.
If you’re looking for an open-deck Subaru engine, make sure to replace the original head gasket with a multi-layer steel unit and keep up with cooling system maintenance to prevent blowing the engine. It may also be worth having a mechanic check it out before you buy to ensure the engine is in good shape as it sits.
Semi-closed deck Subaru engines feature a support piece between the cylinder and the engine block. It still allows for open coolant flow, but provides more strength inside the engine, boosting durability. This is the engine type used in today’s Subaru lineup and has helped the brand establish a reputation for reliability.
Finally, the closed deck engine setups are available only on the older EJ20 Subaru engines and are hard to find these days. These engines are the strongest, but getting one isn’t an easy task, and modern mod support is difficult.
Which engine is in your Subaru?
If your Subaru is from 2005 or later, chances are you have a semi-closed deck engine under the hood. That means you’ve got less worry about problems with head gaskets, and tuning potential is higher than in the older cars. For those with open-deck engines, understanding their maintenance needs may help you avoid headaches in the future.