The EJ25 is Subaru’s 2.5-liter boxer four, used naturally aspirated in Imprezas, Legacys, Outbacks and Foresters from the late 1990s to the early 2010s, and turbocharged as the EJ255 and EJ257 in the WRX, STI, Forester XT and Legacy GT. The most commonly reported EJ25 problems are external head gasket leaks on non-turbo engines, and ringland failure, rod bearing failure and oil starvation on turbo engines, especially modified ones. All EJ25s are interference engines, so a broken timing belt causes valve damage.
Common EJ25 problems
| Problem | Mostly affects | Signs |
|---|---|---|
| Head gasket leaks | Non-turbo EJ25 | Oil and coolant seepage at the head joints, coolant loss, overheating |
| Ringland failure | Turbo EJ255 and EJ257 | Low compression on one cylinder, smoke, blow-by |
| Rod bearing failure | Turbo engines | Knocking that rises with rpm; see spun rod bearing |
| Oil starvation | Turbo engines driven hard | Low oil pressure warnings, bearing damage |
| Timing belt | All EJ25 | Engine stops; valve damage if the belt fails |
EJ25 head gasket problems
Non-turbo EJ25s from the late 1990s through the 2000s are known for head gaskets that seep externally, usually oil first and then coolant, rather than failing suddenly. Watch the coolant level and look for crusty residue at the head-to-block joints. Later, internally leaking gaskets can push combustion gases into the coolant. See Subaru head gasket and ringland failures and signs of a blown head gasket.
Turbo EJ25 problems
The EJ255 and EJ257 make far more power and heat. Ringland failures usually follow detonation from poor fuel, lean conditions or excessive boost, and bearing failures follow low oil or oil starvation. See EJ257 problems and EJ255 vs EJ257.
Timing belt
Replace the timing belt, tensioner and idlers at the interval Subaru specifies. On an interference engine, a failed belt bends valves; see timing belt.
Buying a used EJ25 car
- Look under the car at the head-to-block joints for oil or coolant seepage.
- Ask for timing belt records; an overdue belt is a risk on an interference engine.
- On turbo cars, run a compression test and listen for knocking that rises with rpm.
- Check the oil level; boxers can use some oil, and low oil is a common cause of bearing failure.
Is the EJ25 reliable?
A well-maintained EJ25 with healthy head gaskets, correct oil and a timely belt change can last a long time. Turbo versions need careful warm-up, oil checks and quality fuel.
Replacement and built blocks
Replacement engines are on Subaru EJ25 engines, including IAG short blocks such as the IAG 1150 Series EJ25 short block at $9,499.99. See also EJ25 vs EJ20.
More guides: how long a Subaru engine lasts · head studs vs head bolts · Subaru oil pickup tube · FA20 vs EJ25.
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