2006 JAGUAR XK8

Typical onset: 80,000-140,000 mi

Symptoms: Cold-start misfires that clear up when warm, Progressive loss of compression in one or more cylinders, Excessive oil consumption beyond 1 qt per 1,000 miles, Rough idle and reduced power under load

Fix: Early AJ-V8 engines used Nikasil cylinder liners that degraded with high-sulfur fuel. By 2006 most got steel liners, but some late-build engines or replacement blocks still had the issue. Requires complete engine rebuild with steel liner conversion or short-block replacement. 35-45 hours labor plus machine work if rebuilding in-house, or 25-30 hours for short-block swap.

Estimated cost: $8,000-14,000

Typical onset: 70,000-120,000 mi

Symptoms: Milky pink coolant in expansion tank, Transmission slipping or delayed engagement, Overheating transmission or engine, Coolant loss with no visible external leaks

Fix: The internal transmission cooler in the radiator fails, allowing coolant and ATF to mix. This destroys the transmission if driven. Requires new radiator, transmission flush or rebuild if contaminated, all cooler lines replaced. If caught early before trans damage: 6-8 hours. If transmission is cooked: add 18-25 hours for rebuild.

Estimated cost: $1,800-3,200 early / $5,500-8,500 with trans rebuild

Typical onset: 100,000-150,000 mi

Symptoms: Rattling noise from front of engine on cold start for 2-3 seconds, Check engine light with cam/crank correlation codes, Metallic ticking that worsens with mileage, Rough running or no-start if chain jumps timing

Fix: Plastic chain guides and hydraulic tensioners wear out. If chain jumps, valve-to-piston contact occurs causing catastrophic damage. Preventive replacement of tensioners, guides, and chains on both banks requires 18-22 hours with front-engine disassembly. If valves are bent: add cylinder head work.

Estimated cost: $3,500-5,500 preventive / $7,000-12,000 if valve damage occurs

Typical onset: 90,000-130,000 mi

Symptoms: Deep knocking noise from bottom end, especially under load, Low oil pressure warning at idle when hot, Metallic debris in oil filter and drain pan, Sudden catastrophic failure with oil pressure loss

Fix: Extended oil change intervals or use of wrong viscosity oil leads to bearing failure. Some engines had factory machining tolerances that accelerated wear. Requires crankshaft removal, inspection, and possible machining, plus all bearings replaced. 30-40 hours for complete lower-end rebuild.

Estimated cost: $6,500-11,000

Typical onset: 60,000-100,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Vibration at idle in gear that smooths out in Park/Neutral, Visible transmission sag when inspected on lift, Excessive driveline movement during acceleration

Fix: Hydraulic transmission mounts fail, allowing excessive movement that can stress driveshaft and shifter linkage. Requires transmission support and mount replacement, typically both mounts done together. 3-4 hours labor.

Estimated cost: $650-1,200

Typical onset: 85,000-130,000 mi

Symptoms: Persistent misfire on adjacent cylinders, Coolant consumption without external leaks, White smoke from exhaust on cold start, Compression leakage between cylinders on leak-down test

Fix: Head gaskets fail internally, causing cross-cylinder leakage or coolant intrusion. Both heads should be removed, inspected for warpage, and resurfaced. Includes new gaskets, timing components, and coolant. 22-28 hours labor for both banks.

Estimated cost: $4,500-7,500

Typical onset: 50,000-80,000 mi

Symptoms: Hesitation or stumble during hard acceleration, Engine stalling at idle after highway driving, Difficulty starting when fuel tank below 1/4, Check engine light with lean fuel codes

Fix: In-tank fuel filter clogs from sediment, starving the engine and overworking the pump. Requires tank drop or access through rear seat area depending on design. Replace filter and inspect pump condition. 2-3 hours labor.

Estimated cost: $350-650