The 2004 Forester with the naturally-aspirated 2.5L EJ25 is reliable transportation but infamous for head gasket failure between 80k-150k miles. Transmission cooler and mount issues are secondary but common nuisances.
External Head Gasket Failure (EJ25 SOHC)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: coolant seepage at block/head mating surface visible externally, white crusty residue on engine block below heads, gradual coolant loss without visible leaks elsewhere, overheating if left unattended
Fix: Requires removing both cylinder heads, replacing gaskets with updated multi-layer steel (MLS) type, resurfacing heads if warped. Also replace timing belt, water pump, and all seals while apart. 12-16 labor hours at competent indie shop.
Estimated cost: $1,800-2,800
Transmission Oil Cooler Line Corrosion and Leaks
Common · medium severityTypical onset: 100,000-180,000 mi
Symptoms: ATF drips near radiator or under transmission, pink fluid pooling after parking, low transmission fluid level on dipstick, burnt ATF smell if run low
Fix: Steel lines rust through where they pass near exhaust or mount to radiator. Replace both cooler lines and any corroded fittings. Some shops pre-emptively do this during head gasket job. 2-3 hours labor.
Estimated cost: $300-600
Transmission Mount Failure (Rear/Pitch Stop)
Common · low severityTypical onset: 80,000-140,000 mi
Symptoms: clunk when shifting from reverse to drive, excessive engine rocking on acceleration or deceleration, vibration at idle in gear, visible torn rubber on pitch-stop mount
Fix: Replace rear transmission mount (pitch stopper bracket). Often done alongside transmission cooler lines since access is similar. 1.5-2 hours labor.
Estimated cost: $250-450
Front Lower Control Arm Bushing Deterioration
Occasional · medium severityTypical onset: 120,000-180,000 mi
Symptoms: clunking over bumps, steering wander or vague on-center feel, uneven inner tire wear, failed state inspection for excessive play
Fix: Front lower control arm bushings crack and separate, especially in rust-belt or high-mileage examples. Replace control arms with bushings pre-installed (easier than pressing). Both sides, alignment required. 3-4 hours labor plus alignment.
Estimated cost: $600-900
Exhaust Y-Pipe and Catalytic Converter Rot
Occasional · medium severityTypical onset: 100,000-160,000 mi
Symptoms: exhaust leak noise on cold start, rotten egg smell, check engine light P0420 (catalyst efficiency), visible rust perforation on Y-pipe or cat housing
Fix: Y-pipe and cats are prone to rust-through in salt states. Aftermarket options exist but quality varies. OEM parts expensive. 2-3 hours labor for cat-back or Y-pipe replacement.
Estimated cost: $600-1,400
Wheel Bearing Failure (Front)
Occasional · medium severityTypical onset: 100,000-160,000 mi
Symptoms: growling or humming that increases with speed, noise changes with steering input (louder on turns), ABS light if bearing allows excessive play
Fix: Hub assembly replacement per side. Not serviceable separately on this platform. 1.5-2 hours per side.
Estimated cost: $300-500 per side
Buy one if head gaskets are already done with MLS gaskets and timing belt is fresh; otherwise budget $2-3k within first year of ownership.
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.