Subaru Legacy BM

The 2.0-litre boxer diesel was the first mass-production diesel boxer at all — technically fascinating, but in practice burdened with a string of serious weaknesses. The most severe problem of the early Euro 4 generation is crankshaft failure: the aluminium block has steel inserts in the bearing bridges that tend to crack under stress — total failures sometimes occur between 80,000 and 130,000 km. Later Euro 6 versions are far less affected here. Add the typical modern diesel issues that short trips worsen: a clogged particulate filter, oil dilution from regeneration, a coked EGR cooler with limp mode and a sooted turbo. The timing chain can rattle on cold start. Buyers should prefer a Euro 6 model with long motorway trips in its history and insist on a full service record.

• !! Crankshaft Failure on Early Models (2008-2011) from 100,000 km

  Cracks at the rear main bearing journal from insufficient material strength and incorrect factory torque specs. Failure typically between 50-80k miles, often without warning. Subaru corrected both causes (sealant + torque) after 2011.

  Symptoms: Sudden knocking from engine, oil pressure loss, engine seizure
  4,000–10,000 $
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• !! DPF Clogs on Short Trips from 80,000 km

  Diesel particulate filter clogs with predominantly short-trip driving — regeneration doesn't initiate. Check engine light, power loss, forced dealer regeneration.

  Symptoms: Check engine light, power loss, increased consumption, DPF warning light
  800–2,500 $
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• !! Oil Dilution from DPF Regeneration from 60,000 km

  Frequent DPF regeneration injects diesel into the oil — oil level rises, viscosity drops. Accelerated wear if not changed in time.

  Symptoms: Oil level above max, diesel smell on dipstick, thin oil
  200–1,000 $
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+ 5 more engine weaknesses + vehicle weaknesses

The 2.5-litre NA petrol boxer with a timing chain uses port or direct injection depending on the year. At 125–134 kW it gives enough torque for the mid-size models and is fundamentally solid. The early 2011–2014 builds are affected by the known oil-consumption issue (piston rings, settled by a US class action). Across the years a cam-carrier oil leak appears, whose repair needs the engine out and can run into four figures. The direct-injection units from 2019 tend to coke the valves and have a fragile electronic thermo-control valve whose cracking plastic housing can cause overheating — here too the maker extended the warranty significantly. Otherwise a reliable daily engine with no timing-belt service.

• !! Thermo Control Valve Failure (2019-2022) from 60,000 km

  The direct-injection engines' electronic thermo-control valve (from 2019) has a plastic housing that cracks; coolant vapour destroys the internal electronics. Stuck closed, the engine overheats within minutes. Subaru extended the warranty to 15 years/150,000 miles (part 21319AA010 → 21319AA040).

  Symptoms: Check-engine light with codes P0128/P0125/P26Ax, no or delayed heater warmth, fluctuating coolant temperature, in severe cases sudden overheating.
  1,300–1,800 $
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• !! Oil Consumption — Piston Rings (2011-2014) from 40,000 km

  Class action for 2011-2014 Forester, Legacy, Outback. Piston rings didn't seat due to variable bore roughness. Worst cases: 1 quart per 800 miles.

  Symptoms: Extreme oil consumption, frequent top-ups needed, blue smoke possible
  4,000–6,000 $
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• !! Cam Carrier Seal Leak from 100,000 km

  Known FB engine problem: seal between cam carrier and cylinder head fails. Labor-intensive due to poor access. Service bulletins published.

  Symptoms: Oil stain under engine, oil smell while driving, visible oil seepage at cylinder head
  1,700–6,000 $
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+ 1 more engine weaknesses + vehicle weaknesses

The 3.6-litre flat-six is one of Subaru's most reliable designs and is considered much more durable than the smaller H6 predecessor. Mileages beyond 300,000 km are not rare on cared-for examples. The timing chain is designed for engine life; only the plastic tensioner can develop play at high age. The most common issue is oil leaks: the timing-chain cover is sealed with liquid sealant rather than a gasket, which dries out after many years — a correct reseal is involved and often needs the engine out. The serpentine-belt tensioner also wears over time. Otherwise there are no design weak points. Regular oil changes and checking for damp seals low at the front are important.

• !! Timing Chain Tensioner Worn from 150,000 km

  Plastic timing chain tensioner wears after 90,000+ miles and can no longer maintain adequate chain tension. Starts with cold-start rattle, can progress to timing chain jump. Expensive repair due to many bolts on the chain cover.

  Symptoms: Rattling on cold start, loud chain noise, misfires at high mileage
  1,500–3,200 $
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• !! Timing-cover oil leak from 160,000 km

  The aluminium timing-chain cover is sealed not with a gasket but with liquid sealant. Over time it dries out and the engine seeps oil at the seams, later dripping. A correct reseal often needs the engine out.

  Symptoms: Oil marks on the ground, an oil smell in the bay, seeping seams low on the timing cover, a slowly dropping oil level.
  1,200–2,500 $
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• ! Oil Leaks at High Mileage from 120,000 km

  Valve cover gaskets and timing chain cover become leaky at higher mileage. Typical for boxer engines with many sealing surfaces. Not a critical weakness, but noticeable cosmetically and by smell.

  Symptoms: Oil spots under engine, oil smell when engine is hot
  800–2,000 $
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+ 1 more engine weaknesses + vehicle weaknesses

The 2.5-litre turbo boxer trades revs for displacement: strong torque from low down, plus the typical boxer rumble at idle created by unequal-length headers. Intake-side AVCS smooths the response while the character stays gruff and muscular. Its Achilles heel is the fourth cylinder: the stock intake manifold feeds it worse, it sits furthest from the water pump, runs leaner and hotter — and is the first to crack a ringland under detonation. High-octane fuel and a clean tune are therefore non-negotiable. The rod bearings are sensitive to cold-start full throttle and stretched oil intervals; affected model years got a warranty extension for it. The brazed oil pickup can crack, and the turbo and AVCS banjo screens clog with sludge, causing turbo or cam-timing trouble. With short oil intervals, good fuel, careful warm-ups and clear oil passages it is a long-lived engine.

• !! Ringland Failure — Piston Breakage from 100,000 km

  Cast iron pistons with thin ringlands crack under detonation (knock). Causes: poor fuel quality, bad tuning, high exhaust gas temperatures. The EJ cliché alongside the head gasket.

  Symptoms: Misfires at idle after high-load driving, increasing oil consumption, blue smoke
  3,500–8,000 $
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• !! Rod Bearing Failure from 120,000 km

  Class action for 2012-2017 WRX/STI: extended warranty to 8 years/100k miles. Oil starvation from boxer sloshing or neglected oil level as primary cause.

  Symptoms: Knocking noise, oil pressure warning, metal particles in oil
  3,500–6,500 $
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• !! Oil Pickup Tube Crack from 130,000 km

  Identical problem to EJ205: brazed joint cracks from vibration. No recall despite known issue since 1996.

  Symptoms: Sudden oil pressure drop, engine noise, oil pressure warning light
  3,000–6,000 $
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+ 7 more engine weaknesses + vehicle weaknesses