The 2004 Impreza 2.5L is a solid AWD platform undermined by one catastrophic flaw: head gasket failure. Beyond that, expect typical Subaru transmission mount wear and the occasional speed control cable issue, but the head gasket defines ownership of this generation.
Head Gasket Failure (External Coolant Leaks)
Common · high severityTypical onset: 80,000-120,000 mi
Symptoms: White crusty residue on engine block near head seam, Sweet coolant smell after driving, Gradual coolant loss without visible puddles, Overheating if neglected long enough
Fix: Both head gaskets replacement is mandatory even if only one side leaks currently. Requires engine removal or lifting for proper access. Machine shop resurface heads if warped. 12-16 labor hours plus machine work. Replace timing belt, water pump, and all coolant hoses while you're in there or you're a fool.
Estimated cost: $2,200-3,500
Internal Head Gasket Failure (Combustion Gas into Coolant)
Occasional · high severityTypical onset: 100,000-150,000 mi
Symptoms: Bubbling overflow tank even when cold, Exhaust gas smell from radiator cap, Mysterious coolant consumption with no external leaks, White smoke from exhaust (if severe), Positive combustion gas test
Fix: Same head gasket job as external leak but urgency is higher—combustion pressure cooks coolant and can crack heads. Heads must be pressure-tested and often need surfacing or replacement. 14-18 hours labor. If you drove it overheated, budget for head replacement not just resurface.
Estimated cost: $2,800-5,000
Transmission Mount Collapse
Common · low severityTypical onset: 70,000-110,000 mi
Symptoms: Clunk when shifting from reverse to drive, Excessive engine movement visible from engine bay during throttle blip, Vibration at idle in gear, Notchy shifter feel in manual transmission cars
Fix: Rear transmission mount (pitch stopper) turns to mush. Simple bolt-in replacement. 1.0-1.5 hours. OEM Subaru part strongly recommended over aftermarket—cheap mounts fail in 20k miles.
Estimated cost: $150-280
Front Lower Control Arm Bushing Failure
Common · medium severityTypical onset: 90,000-130,000 mi
Symptoms: Clunking over bumps from front suspension, Wandering steering or pull to one side, Inner front tire wear, Visible cracks or torn rubber in control arm bushings
Fix: Front lower control arm bushings rot out. Most shops replace entire control arms rather than press bushings—easier and not much more expensive. Alignment mandatory after. 2.5-3.5 hours labor per side, usually do both.
Estimated cost: $450-750
Cruise Control Cable Detachment/Fraying
Occasional · low severitySymptoms: Cruise control inoperative, Throttle sticking open momentarily (rare but dangerous), Visible fraying at throttle body or under hood
Fix: Speed control cable can fray or detach at throttle body. Inspect during oil changes. Replacement is straightforward cable swap. 1.0-1.5 hours. NHTSA had a recall but many cars missed it—check VIN for open campaigns.
Estimated cost: $180-320
Transmission Oil Cooler Line Corrosion (Automatic)
Occasional · medium severityTypical onset: 100,000+ mi or salt-belt cars earlier
Symptoms: Red ATF fluid dripping near radiator, Low transmission fluid level, Transmission slipping or delayed engagement if fluid level drops critically
Fix: Steel ATF cooler lines rust through on salt-belt cars. Replace lines, refill and flush transmission fluid. 2.0-3.0 hours. Catch it early or you're buying a transmission.
Estimated cost: $350-600
Great AWD platform if you budget $3k for inevitable head gaskets or find one already done with receipts—otherwise it's a ticking time bomb that will strand you.
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.