2017 SUBARU WRX STI

Typical onset: 40,000-80,000 mi

Symptoms: Sudden misfire on cylinder 4, White smoke from exhaust, Loss of compression on #4, Knock/rattle from engine, Check engine light with P0304 code

Fix: EJ257 pistons crack between compression ring and oil ring land, usually on cylinder 4 due to leaner AFR. Requires full engine rebuild or short block replacement. 18-25 labor hours for proper rebuild with forged internals, or 12-16 hours for OEM short block swap.

Estimated cost: $6,000-12,000

Typical onset: 60,000-120,000 mi

Symptoms: Loud knocking on cold start that persists, Metal shavings in oil, Oil pressure fluctuations or drop, Catastrophic bearing noise under load

Fix: EJ257 bearing tolerances are tight and oil starvation from hard cornering, delayed oil changes, or low oil level leads to bearing damage. Requires crankshaft inspection, possible resurfacing, and bearing replacement minimum. Often discovered during diagnosis of knock. 15-22 labor hours depending on crank condition.

Estimated cost: $4,500-8,500

Typical onset: 70,000-110,000 mi

Symptoms: Transmission fluid leak at front of vehicle, Burned fluid smell, Difficulty shifting when hot, Fluid visible on crossmember or skid plate

Fix: Hard lines to transmission cooler corrode where they route near exhaust or chassis contact points, particularly on salted roads. Lines must be replaced as assembly. 2-3 labor hours, straightforward job but requires lift access.

Estimated cost: $400-700

Typical onset: 60,000-100,000 mi

Symptoms: Clunk when shifting from reverse to drive, Excessive driveline movement felt through shifter, Visible torn rubber on mount inspection, Harsh engagement into first gear

Fix: Pitch stop mount (rear transmission mount) tears from hard launches and aggressive driving. Direct replacement, 1.5-2 labor hours. Upgraded polyurethane mounts available and recommended.

Estimated cost: $250-450

Typical onset: 80,000-140,000 mi

Symptoms: Oil seepage visible on block exterior, Slight coolant smell but no overheating, Crusty buildup where heads meet block, Oil consumption without visible leaks elsewhere

Fix: While not the catastrophic internal failure of older EJs, external weeping still occurs. Requires head removal, resurfacing, and MLS gasket installation. 12-16 labor hours for both sides. Often combined with timing components and water pump.

Estimated cost: $3,200-5,000

Symptoms: Hissing sound under boost, Loss of boost pressure, Check engine light for boost leak, Visible crack in plastic Y-pipe

Fix: Plastic turbo inlet pipe cracks at stress points from heat cycles and engine movement. Aftermarket aluminum replacements widely available and superior. 1-1.5 labor hours, intake removal required.

Estimated cost: $300-600