The 2.5-liter engine Subaru EJ251 was produced at the Japanese company from 1998 to 2004 and was put almost on the entire model range of the concern at that time: Impreza, Legacy and Forester. For markets with strict environmental requirements, a version with the index EJ252 was offered.
The EJ25 range also includes EJ25D, EJ253, EJ254, EJ255 and EJ257.
Subaru EJ251 2.5 liter engine specifications
| Characteristics | Reference |
|---|---|
| Fine volume | 2457 cm³ |
| Power system | Injector |
| Drive power | 165 hp |
| Torque | 225 Nm |
| Cylinder block | Aluminum H4 |
| Cylinder head | Aluminum 16v |
| Cylinder diameter | 99.5 mm |
| Piston stroke | 79 mm |
| Compression ratio | 10 |
| Drive Features | SOHC |
| Hydrocompensators | No |
| Transmission timing | Belt drive |
| Fasoregulator | No |
| Turbocharger | No |
| What oil to use | 4.2 liters 5W-30 |
| Environmental class | Euro 2/3 |
| Example service life | 280,000 km |
| Engine weight | 130 kg |
Cars on which the Subaru EJ251 2.5 liter engine was installed:
- Subaru Impreza 1 (GC) – 1998 – 2000
- Subaru Impreza 2 (GD) – 2000 – 2003
- Subaru Forester 1 (SF) – 1998 – 2002
- Subaru Forester 2 (SG) – 2002 – 2004
- Subaru Legacy 3 (BE) – 1998 – 2003
- Subaru Outback 2 (BH) – 1998 – 2004
- Subaru Baja 1 (BT) – 2002 – 2005
Subaru EJ251: problems, breakdowns
EJ251 is one of the most massive Subaru 2.5 liter atmospheric opposition engines. It was installed on Subaru Legacy, Outback, Forester and Impreza in the late 1990s and early 2000s. Despite the simple design and not bad reliability on paper, in practice this engine turned out to be rather capricious and demanding to service.
Excessive oil consumption
One of the most frequent complaints of owners is oil consumption. Even with moderate operation, the engine can consume from 0.5 to 1.5 liters of oil per 1000 km, especially closer to 200 thousand km of mileage. Causes:
Piston ring wear.
Carbon monoxide through the valve guides.
Constant leaks through oil seals and gaskets, including valve covers and lobes.
Liner rotation
If a falling oil level is ignored, it can lead to oil starvation and rotten crank liners. The engine starts knocking, loses oil pressure quickly and can seize up on the road. Regular level checks are vital.
Overheating and an inefficient cooling system
The EJ251 runs at high temperatures and the cooling system, especially on first editions, is not always up to the task:
- The radiators become clogged over time.
- The pumps lose performance.
- Air plugs appear and are difficult to drain without special skills.
All this leads to overheating, and an overheated block is one of the typical woes of the EJ family.
Crankcase gasket problems
A very well known problem with EJ251 motors is the “breakdown” of the head gaskets. The gaskets start to leak:
- Either oil into the coolant (emulsion on the cap),
- or coolant into the cylinders (white smoke).
- or squeezes antifreeze outward.
Early batches used dual layer composite gaskets, which degraded quickly. Subaru later replaced them with multi-layer metal (MLS) gaskets, which partially solved the problem.
Cylinder 4 knocking
As with many Subaru opposition engines, the EJ251’s 4th cylinder suffers more than the others, as it has poorer cooling. Frequent overheating can deform the block or scuff the cylinder wall. The result is knocking, reduced compression, and rapid wear.
Recall Campaigns and Technical Bulletins
There have been no global recall campaigns on the EJ251 engine itself, but there have been several important service bulletins (TSBs):
Crankcase gaskets
Subaru officially recognized a problem with the head gaskets on EJ251 engines, especially on 1999-2002 vehicles. Instructions were issued for:
- Checking the condition of the coolant for carbon monoxide.
- Early diagnosis of leaks.
- Recommended replacement of gaskets with updated MLS packages.
Cooling System
Some bulletins addressed proper cooling system pumping and thermostat replacement. Subaru recommended not using non-original thermostats as they often opened at the wrong temperature.
Oil pump problems
A portion of the vehicles had oil pressure overflow on cold and leakage across the pump housing. Subaru offered to replace the casing or gaskets as part of the maintenance.
Conclusion
EJ251 is a motor capable of a long resource, but only with constant attention and careful operation. It is not forgiving:
- Overheating,
- low oil level.
- Lack of maintenance.
Regular oil changes, cooling system checks, and preventative replacement of problem gaskets can all extend the life of your engine. Otherwise, you’ll quickly end up with a knocking 4th cylinder, an overheated block, and a contract motor.