The 2006 Forester with the 2.5L NA engine is generally reliable, but the notorious head gasket weep is almost inevitable, and transmission cooler line corrosion leads to internal trans damage if ignored—both are expensive repairs that define ownership of this generation.
External Head Gasket Leaks (Oil Seepage)
Common · medium severityTypical onset: 90,000-150,000 mi
Symptoms: Oil residue on sides of engine block below heads, Burning oil smell after driving, Gradual oil consumption increase, Visible seepage at head/block mating surface
Fix: Replace both head gaskets while engine is apart; resurface heads if warped. Budget 12-16 labor hours. Do timing belt, water pump, and all external seals while you're in there—otherwise you're paying twice. This is a when-not-if item on these EJ253 motors.
Estimated cost: $1,800-2,800
Transmission Oil Cooler Line Corrosion and Failure
Common · high severityTypical onset: 100,000-180,000 mi
Symptoms: Pink ATF dripping from bellhousing area or radiator, Transmission slipping or delayed engagement after leak starts, Rust perforation visible on steel cooler lines along chassis, Low ATF level on dipstick
Fix: Replace corroded steel cooler lines with updated parts (some use braided aftermarket lines). If ATF mixed with coolant through radiator leak, flush both systems immediately or expect transmission failure within weeks. Line replacement alone is 2-3 hours; if trans is damaged, you're looking at rebuild or replacement, 8-12 hours labor.
Estimated cost: $300-800 (lines only); $2,500-4,000 (if trans rebuild needed)
Front Lower Control Arm Bushing Failure
Common · medium severityTypical onset: 80,000-130,000 mi
Symptoms: Clunking over bumps from front suspension, Wandering steering or vague handling, Visible torn rubber bushings at control arm pivot points, Uneven inner tire wear
Fix: Replace front lower control arms as assemblies (bushing replacement alone often not worth the press work). Most techs do both sides for even wear. 2.5-3.5 hours labor for the pair. Alignment required after.
Estimated cost: $500-900
Rear Wheel Bearing Failure
Occasional · medium severityTypical onset: 120,000-180,000 mi
Symptoms: Humming or growling noise from rear that increases with speed, Noise changes pitch in turns, Vibration through body at highway speed, ABS light may illuminate if bearing is severely damaged
Fix: Replace wheel hub/bearing assembly (non-serviceable sealed unit). Single side is 1.5-2 hours; if both are noisy, do them together. Fronts wear too but rears tend to go first on this generation.
Estimated cost: $350-550 per side
Crankshaft Position Sensor Failure
Occasional · high severitySymptoms: No-start condition, engine cranks but won't fire, Stalling at idle or while driving, then won't restart until cool, Check engine light with P0335 code, Intermittent starting issues that become more frequent
Fix: Replace crank sensor at back of engine near flywheel. Access is tight; 1.5-2 hours labor. Keep a spare in the glovebox if you're over 150k miles—it's a cheap insurance policy against being stranded.
Estimated cost: $200-350
Transmission Mount Deterioration
Occasional · low severityTypical onset: 100,000-160,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible cracking or separation of rubber mount, Driveline shudder on acceleration from stop
Fix: Replace rear transmission mount (pitch stopper). Simple job, 0.8-1.2 hours. Often overlooked but makes a big difference in drivability. Check all motor mounts while you're diagnosing this—they're the same age.
Estimated cost: $180-300
Solid winter vehicle and great value used, but factor $2,000-3,000 into purchase price for the inevitable head gasket job if it hasn't been done—confirm service history or walk away from high-mileage examples without documentation.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.