The 2002 XJ8 with the 4.0L AJ-V8 is a refined luxury sedan plagued by Nikasil engine bore failures and transmission cooler issues that can turn catastrophic. Beautiful cars when running, but high-stakes ownership after 80k miles.
Nikasil Cylinder Bore Failure (Pre-2000 Engine Carryover)
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: Excessive oil consumption (quart per 500-1000 miles), Cold-start misfires that clear when warm, Loss of compression on multiple cylinders, Blue smoke on deceleration
Fix: Complete engine rebuild with Nikasil-free steel liner block or replacement long block required. 25-35 labor hours including removal, installation, fluids, timing components. Many owners opt for salvage engines from post-2000 model years with steel liners.
Estimated cost: $6,500-12,000
Transmission Oil Cooler Line Failure
Common · high severityTypical onset: 70,000-120,000 mi
Symptoms: Coolant mixing with transmission fluid (strawberry milkshake in reservoir), Transmission slipping or delayed engagement, Coolant loss with no external leaks, Transmission overheating warnings
Fix: Internal cooler in radiator fails, requires radiator replacement, complete transmission flush (often multiple flushes), new transmission filter. If caught late, transmission rebuild needed. 6-8 hours for cooler/radiator/flush; add 18-25 hours if transmission damaged.
Estimated cost: $1,200-2,500 (if caught early), $4,500-7,000 (with transmission damage)
Timing Chain Tensioner and Guide Wear
Occasional · high severityTypical onset: 80,000-130,000 mi
Symptoms: Rattling noise on cold start that subsides after 10-15 seconds, Check engine light with cam/crank correlation codes, Metallic noise from front of engine at idle, Sudden loss of power or no-start if chain jumps
Fix: Both banks require tensioners, guides, chains. Front-engine access intensive work. 18-24 labor hours including valve cover gaskets, front cover seals, cam phaser inspection. Do water pump and thermostat while in there.
Estimated cost: $3,500-5,500
Rear Differential Bushing Failure
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Clunking when accelerating from stop, Vibration at highway speeds, Differential sitting visibly low or cocked to one side, Driveline shudder during shifts
Fix: Rear subframe bushings and diff mounts deteriorate. Differential must be lowered, bushings pressed. 5-7 labor hours. Replace all four subframe bushings at once, not just failed side.
Estimated cost: $1,200-1,800
Air Suspension Compressor and Line Failures
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Vehicle sits low after sitting overnight, Compressor runs constantly (hear pump under right rear), Suspension fault warning on dash, One corner sags while others stay up
Fix: Compressor wears out from overwork due to leaking air springs or lines. Compressor replacement 2-3 hours. If springs or lines leaking, add 1-2 hours per corner. Many owners convert to coil springs ($800-1,200 parts/labor) rather than chase leaks.
Estimated cost: $1,500-2,200 (compressor only), $2,500-4,000 (compressor plus multiple air springs)
Throttle Body Failure
Occasional · medium severitySymptoms: Intermittent limp mode with reduced power, Idle surging or stalling, Throttle response lag or sticking, Check engine light with throttle position sensor codes
Fix: Electronic throttle body assembly fails, cannot be rebuilt. Replace unit, relearn procedure required. 1.5-2 hours labor. Use OEM or quality remanufactured unit—cheap aftermarket throttles cause repeat issues.
Estimated cost: $600-1,000
Steering Rack Leaks
Occasional · medium severityTypical onset: 80,000-120,000 mi
Symptoms: Power steering fluid leak visible on inner tie rods or rack boots, Groaning noise when turning at low speeds, Steering feels notchy or stiff when cold, Fluid level drops repeatedly
Fix: Rack seal failure at 100k+ miles. Rack replacement requires front subframe lowering. 7-9 labor hours including alignment. Rebuilds available but replacement more reliable long-term.
Estimated cost: $1,800-2,800
Buy only if engine provenance is confirmed and you have a $5k repair fund—spectacular to drive but Nikasil and cooler failures make this a gamble for average DIYers.
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.