The 1998 Impreza is a reliable compact AWD platform, but the 2.5L models suffer from notorious head gasket failures while the 2.2L is nearly bulletproof. Transmission mounts wear prematurely across all variants, and these older Subarus demand vigilant cooling system maintenance.
2.5L Head Gasket Failure (Phase I EJ25D)
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: External coolant seepage at head/block junction, White exhaust smoke on cold start, Coolant consumption with no visible leaks, Overheating under load, Milky oil on dipstick (if internal leak progresses)
Fix: Requires cylinder head removal, new MLS gaskets, resurfacing heads if warped (common), and timing belt service while apart. Budget 12-16 labor hours. Do NOT reuse single-layer gaskets—only multi-layer steel replacements. The 2.2L does not have this issue.
Estimated cost: $1,800-2,800
Transmission Mount Collapse
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Clunking when shifting from reverse to drive, Excessive drivetrain movement on acceleration, Vibration at idle in gear, Visible rubber deterioration on rear trans crossmember mount
Fix: The rear transmission crossmember mount fails predictably due to heat and load cycles. Replace with OEM or upgraded polyurethane bushings. 1.5-2 hours labor, straightforward job but requires lifting the transmission slightly.
Estimated cost: $180-350
Valve Cover Gasket Oil Leaks
Common · low severityTypical onset: 70,000-120,000 mi
Symptoms: Oil seepage along valve cover perimeter, Burning oil smell after hard driving, Oil residue on exhaust manifolds, Low oil level between changes
Fix: Boxer engines make valve covers difficult to access—requires removing multiple intake and ignition components. Replace both sides simultaneously along with spark plug tube seals. 3-4 hours labor for both banks.
Estimated cost: $400-650
Front Wheel Bearing Failure
Occasional · medium severityTypical onset: 90,000-140,000 mi
Symptoms: Grinding or humming noise that changes with speed, Noise increases in turns (load-dependent), Wheel play when jacked up, ABS light may illuminate on later models
Fix: The front hub assemblies wear faster than competitors due to AWD loads. Press-in bearings require proper tools—this isn't a hammer job. Replace both sides if one fails after 100k. 2-3 hours per side including alignment check.
Estimated cost: $350-600 per side
Rear Differential Carrier Bearing Noise
Occasional · medium severityTypical onset: 100,000-150,000 mi
Symptoms: Whining or growling from rear on acceleration, Noise pitch changes with speed, not engine RPM, Metallic grinding if severely worn, Gear oil contamination with metal particles
Fix: Rear diff carrier bearings fail from inadequate fluid changes (should be every 30k). Requires complete disassembly, bearing replacement, and careful setup with shims and preload tools. 6-8 hours labor. If caught early, just bearings; if neglected, ring and pinion damage adds $500+ in parts.
Estimated cost: $800-1,400
Fuel Filter Clogging (Leading to Pump Failure)
Occasional · medium severityTypical onset: null
Symptoms: Hard starting when hot, Loss of power under load or at highway speeds, Sputtering or hesitation during acceleration, Check engine light with lean fuel trim codes
Fix: The inline fuel filter (under car near tank) clogs from sediment buildup if never replaced—Subaru didn't emphasize this service. Clogged filter overworks the in-tank pump, causing premature failure. Replace filter every 60k miles. Filter alone: 0.5 hours. If pump fails: 3-4 hours to drop tank.
Estimated cost: $80-150 (filter only), $600-900 (pump replacement)
Timing Belt and Water Pump
Common · high severityTypical onset: 105,000 mi intervals
Symptoms: No symptoms until catastrophic failure, Coolant weeping from water pump weep hole (advance warning), Squealing from worn idlers before belt fails
Fix: Interference engine—belt failure destroys valves and pistons ($3,000+ rebuild). Replace at 105k intervals with water pump, idlers, tensioner, and camshaft/crankshaft seals. Do NOT skip the water pump—they fail at similar mileage and require the same labor. 4-6 hours for full service.
Estimated cost: $600-1,000
Buy a 2.2L model without hesitation; approach 2.5L models only with proof of head gasket replacement using upgraded parts—otherwise budget $2,000 immediately.
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.