Subaru EJ Engines: Head Gasket, Ringland, Timing Belt Risks

Jalopnik has a rundown on why Subaru's EJ family of boxer engines earned a bad reliability reputation, and it comes down to the engine's design.

The EJ series powered a range of Subaru models: the EJ205 appeared in early 2000s Japanese-market WRXs. The EJ255 showed up in versions of the WRX, Forester XT and Legacy GT through 2014. The EJ257 powered the WRX STI from 2004 to 2021. Because the pistons sit horizontally opposed, they move side to side instead of up and down. That layout creates specific problems.

Head gaskets

EJ25 engines had the worst head gasket reputation. According to Jalopnik, the gaskets sit vertically at the bottom of each side, so oil can saturate the material when the engine is off instead of draining back into the pan. Older engines used a porous gasket that let coolant seep through; later multi-layer steel gaskets could tear or corrode. A leaking head gasket can cause poor compression, overheating and white smoke from the tailpipe. The issue hit Legacy, Outback, Forester and Impreza models from the late 1990s through the mid-2010s.

Piston ringland failure

Search "piston ringland" and Subaru engines fill the results, Jalopnik notes. The ringlands sit below the piston crown and seal combustion gases while scraping oil off cylinder walls. When the top ringland can't seal, power drops, combustion gases blow by, and oil burns off faster.

Jalopnik says the causes are mixed: thin, brittle piston material, excessive heat from modified engines, and detonation from low-octane fuel. The EJ257 is tuned for higher-octane gas, and lower-octane fuel can cause knocking. Add an aftermarket turbo and middling octane, and knock can shock the ringlands into failure. Damaged ringlands can score cylinder walls, leading to more engine damage.

EJ engines also burn oil, and very high consumption can signal ringland failure. The boxer layout makes oil starvation more likely in hard cornering, because oil can move away from the pickup tube, and the oil pump may suck air. Oil pump failures are not rare in EJs, Jalopnik adds.

"Don't let your Subaru run dry of oil!" Jalopnik advises.

Timing belt

The EJ uses a timing belt, not a chain, and it's an interference engine. If the belt breaks or jumps, pistons can hit valves and destroy the engine. Subaru recommends a timing belt replacement at 105,000 miles. Jalopnik suggests owners consider doing it sooner.

• EJ engine
• head gasket
• piston ringland
• reliability
• Subaru
• timing belt